Custard Fruit Tart: Don't Lose Your Temper

With the warmer weather (finally) trickling in, what better to celebrate with than a fresh fruit tart? (Lots of things, particularly sangria, but I made a tart.) I love the spring/summer because it generally means that you can get lots of my favourite fruit, strawberries, for cheap. While good berries don't generally need an accompaniment, this tart is probably as refreshing as just the berries because it's served cold, but it's way more indulgent because of the rich custard the fruit is served upon. Supporting this delicious combination is a sweet cookie-like crust that makes the tart easy to pick up (although I usually manage to break it upon serving so it's best to have some forks on hand). This recipe takes a bit of idle time (as there's cooling involved) so it's perfect if you're spending the day at home.

I should probably stop taking photos in my kitchen at night. The lighting is super weird.

What you'll need:

Fruit, flour, sugar (powdered and granulated), milk (either whole milk or a milk-cream combination), eggs, cornstarch, butter, and vanilla. Also salt.

This recipe can be divided into two and a half components. The half is the fruit step, because washing and slicing fruit is distinct from the other heat-demanding parts, but can hardly be considered a step. Come on.

First will be the preparation of the crust/tart shell. You'll need a tart pan in the 8-10 inch range (preferably with removable bottom for easy removal) and some aluminum foil for this. Butter the inside of the pan as well as a piece of foil big enough to cover it. The pan I used is nonstick, but the butter helps with browning. Yum.

It's easiest to just take a chunk of butter and smear it all over with your fingers. You're at home, no one's judging you.

Take the flour, icing sugar, salt, and butter in a medium-sized bowl and mash them together. If you don't have a pastry blender, a big fork works too. Try not to use your fingers because they'll warm up the butter, and you want to keep it as cold as possible (plus, you'll get the dough all over your hands if you forgo the fork). Once you're done that, mix in an egg yolk until just combined. 

This is much easier to do in a food processor, but I don't own one.

The resulting dough will be pretty sandy. If you want your crust flakier, cut in some more butter or some shortening. I like mine to be more like a fancy cookie (and with the amount of the custard, it helps to have a strong base). Whatever you end up going with, dump the dough into your tart pan.

If you're taking pictures of your food like me, wipe up the mess you made on the counter trying to get all of the dough in the pan.

Take a measuring spoon or a sturdy glass and gently press the dough into the sides, keeping the thickness of the dough the same throughout (even the sides, which is frustrating). Don't press too firmly or your shell will become rock-hard.

I didn't manage to get it all the way up the sides. Life's full of disappointment, kids.

Take a fork and poke holes throughout the dough. This is called docking (probably, I'm not sure that professionals use dinner forks) and it helps prevent bubbles by providing steam a place to escape.

If you don't do a good job here, don't worry. It'll all be covered up anyway.

Wrap it up in aluminum foil (butter-side down) and freeze it for 30 minutes while you make the custard filling.

For the custard:

Slowly heat up the milk in a medium saucepan on low, until simmering but not boiling. Stir it occasionally with a whisk to prevent a skin from forming.

Combine the sugar and cornstarch in a measuring cup with a fork. Try to use one with a capacity of at least 2 cups. The measuring gradations aren't essential, but the spout helps prevent sticky messes on your counter.

You can proceed with custard-making or you could try selling it on the street. I wouldn't advise the latter.

Add the eggs and mix until it turns into a sort of slurry.

Mmm. Gritty eggs.

Drizzle about a third of the milk into the eggs, stirring constantly. Then, pour the eggs into the milk (which is still being heated on low) slowly, whisking constantly. Yes, constantly. I know. It's the worst.

Special thanks to my roommate, who took photos of this process while making fun of me.

What we're doing here is tempering the eggs to slowly raise the temperature before they cook. This step appears to be pretty pointless, but it serves an important purpose. When you add eggs to hot milk, they'll get super gross and you'll have scrambled eggs floating in milk. Please don't serve this to your guests. This tempering step is required (or at least, strongly advised) because of the proteins in the eggs. Without tempering, the temperature would change drastically very quickly, the egg proteins would clump together and solidify during cooking, and you wouldn't have custard. 

The sugar and cornstarch in this mixture also help prevent curdling. By adding them to the eggs before cooking, they keep the egg proteins from aggregating by just getting in the way of the proteins. The sugar's also there for flavour. The cornstarch acts as a thickener, with starch molecules forming a network that keeps both the milk proteins and egg proteins from sticking together, while providing some structure to the final custard without really affecting much of the taste. 

Why it's important not to overheat low-fat milk:

Milk has 3 main components: water, milk protein, and fat (lots in butter, hardly any in skim milk). In most cases, all of these hang out in the form of a colloid, which is kind of like a solution, except that rather than dissolving, the constituents are just too small to really separate out well. The proteins' resting state (without changes to their pH or temperature) is their native conformation. When it's heated, the proteins unfold, and are considered denatured. If they have a specific role in biochemical reactions, these proteins are less able, if at all, to perform this function.

Generally, cream can be taken to higher temperatures without terrible consequences. However, when lower fat milk is heated too hot, the proteins will curdle and form clumps. This is good for cheese and buttermilk, but not so good for a smooth custard.

Adding cornstarch helps prevent this curdling. The amounts we're adding won't really have much of an effect on the temperature, but it will help by adding starch molecules, which form a net that keeps the proteins away from one another. Fat globules within higher-fat milk or cream help serve a similar function, but I didn't have enough whipping cream for that.

Tempering eggs:

Normally, the proteins in eggs (there are multiple kinds, but for our purposes, they're all orange squiggles) exist within the liquid individually, in a more or less defined conformation. When you heat eggs, the proteins become denatured (ie. they unfold).

If enough heat is applied, these proteins will bunch up into little aggregates, or clumps, and separate out from the other stuff. In this case, water and fat.

When the proteins aggregate, the egg is cooked (or in this case, curdled). In a custard, we don't want the egg proteins to bunch up like this, as it will produce scrambled eggs in a milk bath. Yuck.

However, if you temper them and increase their heat slowly while mixing them, the egg proteins won't bunch up with one another so tightly. There will still be some combining, but it won't be so separate from the rest of the constituents and the bonding will actually add structure to the resultant custard. 

When the custard becomes about as thick as whipped cream (you'll have a harder time getting the whisk through), pour it through a sieve into a bowl and stir in the vanilla.

The sieve sucks to wash when it's full of custard.

Let it sit for a few minutes, then stir in the butter.

Recipes apparently call for it to be added slowly. It doesn't really make a difference in this case.

Move the custard into a smaller bowl, smoosh some plastic wrap over the top to minimize air exposure, and cool in the fridge for a few hours.

"Smoosh" is a technical term, of course.

With the custard done (if at least half an hour has passed), you can bake the crust for 25 minutes, then remove the foil and bake for an additional 8 minutes or until light golden brown. Let cool completely before filling.

This is what it looks like before it goes in the oven. I forgot to take a picture of the after.

The next parts are incredibly simple. Wash the fruit and, in the case of larger fruits like strawberries, kiwis, etc., cut in half or into thirds or slices. Use the strawberries to cover the tart, but if you ate too many so you don't have enough strawberry halves to cover the tart, then just slice them up so they look pretty. Dry excess water from the fruit with a paper towel so the tart doesn't get goopy.

Take the (cooled!) tart shell and the chilled custard, and spread the custard out over the shell. If you have too much, don't try to force it. Just eat the custard by itself, with fruit or nuts or whatever. It's like indulgent yogurt, which is my kind of yogurt. Without the probiotics.

You can't see it, but I got a stomachache from eating too many strawberries before this step.

Then, just cover with fruit. Arrange it so it looks pretty. Or don't. I did.

The lighting in this photo is super weird. I don't know why.

If you're carrying the tart somewhere, you may want to use a glaze. I've never made one, but I like heating up some apple jelly over the stove and pouring it over. Works the same (probably) and tastes great.

Enjoy!

Custard Fruit Tart

Shell: 

1 1/2 cups flour

1/2 cup icing sugar

1/4 tsp salt

3/4 cup butter

1 large egg yolk

Cut everything except the egg yolk together in a large bowl with a pastry cutter or fork (or in food processor). Mix in yolk.

Knead together lightly. If it won't come together like wet sand, add a tablespoon of cold water.

Press into a buttered 8-10 inch tart pan, prick throughout with fork and freeze for at least 30 minutes. If you want to roll it instead, freeze it in a brick for 2 hours then roll out.

To bake, preheat oven to 375 degrees F and bake for 25 minutes. Remove the foil and press the crust in with a fork if it has puffed up. Return to oven and bake another 8 minutes or until light golden brown. Cool to room temperature before filling.

Pastry Cream/Custard Filling

2 cups whole milk (or 4 tbsp heavy cream + 1 3/4 cups milk)

1/2 cup sugar

2 large eggs

1/4 cup unsalted butter

1/4 tsp salt

3 tbsp cornstarch

1 tsp vanilla extract

Pour milk into a medium saucepan, add salt, bring to a simmer, stirring occasionally (do not boil).

Whisk together cornstarch and sugar, whisk in eggs until smooth.

When milk is ready, slowly drizzle in a third into the egg mixture, whisking continuously.

Add the milk/egg mixture back into the saucepan until as thick as whipped cream (about 2 minutes). Do not let boil.

Remove from heat, pour into sieve, stir in vanilla.

Let cool 10 minutes, stirring occasionally.

Cut butter into 1 tbsp pieces and whisk into custard. Cover tightly with plastic wrap pressed over surface and chill thoroughly.

To fill:

Wash and cut large berries into halves or slices, slice larger fruits. Remove chilled custard and spread over room temperature shell. Arrange fruit. If desired, heat up apple jelly on stove in small saucepan over medium heat. Pour over tart and refrigerate. Serve chilled.