Ingredients

Custard:
3 large egg yolks
1/2 cup heavy cream
1/2 cup milk
1/4 cup vanilla sugar or granulated sugar
1 1/2 tablespoons cornstarch
Cake & Assembly:
1 cup plus 2 tablespoons cake flour
3/4 cup plus 1 tablespoon granulated sugar, divided
1 1/2 teaspoons baking powder
1/2 teaspoon kosher salt
2 large egg yolks, room temperature
1/2 cup vegetable oil
6 tablespoons water
1/2 teaspoon finely grated lemon zest
1/2 teaspoon vanilla extract
4 large egg whites, room temperature
1/4 teaspoon cream of tartar
1 1/2 pounds strawberries
1 cup chilled heavy cream
2 teaspoons powdered sugar

Instructions

In a small saucepan over medium-low heat, whisk the egg yolks, cream, milk, granulated sugar, and cornstarch, reducing the heat if the mixture starts to simmer, until thickened. Transfer the custard to a bowl, cover with plastic wrap, and let cool to room temperature. Transfer to the refrigerator and chill for at least 3 hours or up to 2 days.
Heat the oven to 325°F. Line the bottom of a 13-by-9-inch pan with lightly oiled parchment paper. In a large bowl, whisk the flour, ½ cup of the granulated sugar, the baking powder, and salt.
Using an electric mixer on medium-high speed, in a medium bowl, beat the egg yolks, oil, water, lemon zest, and vanilla until smooth. Stir into the flour mixture. Using the electric mixer on medium-high speed, in another large bowl, beat the egg whites with the cream of tartar until soft peaks form. Add ¼ cup of the granulated sugar and beat on high speed until the peaks are stiff but not dry.
Using a rubber spatula, fold about one-quarter of the fluffy egg whites into the egg yolk mixture. Very gently fold in the remaining egg whites. As soon as the egg whites are no longer visible, stop folding. Scrape the batter into the prepared pan and spread evenly. Bake for about 35 minutes, until the top springs back when lightly pressed and a tester inserted into the center comes out clean. Let cool in the pan on a wire rack for at least 1 hour.
Meanwhile, hull and thinly slice the strawberries. Sprinkle with 1 tablespoon of the granulated sugar and toss to coat. Let the strawberries macerate, stirring occasionally, for about 1 hour.
Using the electric mixer on medium-high speed, in a medium bowl, whip the cream and powdered sugar together until stiff peaks form, making sure not to overwhip (or else you'll be making butter!).
When the cake is cool, run a knife around the sides and lift the cake from the pan using the parchment. Transfer to a cutting board.
Using the lid of a Mason jar as a template, cut out 10 (I was able to get 11, but 10 is a nicer, round number) cake circles, making sure to cut slightly inside the outline so the cake will fit inside the jar. Tear the remaining cake scraps into large crumbs (you will use this for the middle layer of each jar).
Slice each cake circle in half horizontally. Place the bottom half in the bottom of a half-pint jar. Top with a spoonful of the sliced strawberries (including some juices), then a spoonful of the custard. Tap the jar a few times to make sure everything is settled. Top with a layer of the cake crumbs, then another layer of the strawberries and custard. Place the top half of the cake circle on top of the second layer of custard. Top it all off with a dollop of the whipped cream.

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