For The Vanilla Custard Filling:
3 large egg yolks1/4 cup granulated sugar2 Tablespoons cornstarch1 cup whole milk1 Tablespoon unsalted butter1 teaspoon vanilla extract1/4 cup heavy cream
In a medium bowl, whisk together the yolks, sugar and the cornstarch, set aside.
In a medium saucepan, bring the milk to a gentle boil. Remove the pan from the heat and whisk about 1/3 cup of the hot milk into the yolk mixture. Return the entire mixture to the saucepan, place over medium-high heat, and bring to a boil, whisking constantly, for 1 minute. Remove the pan from the heat, scrape the bottom of the pan with a spatula, and whisk until smooth. Whisk in the butter until melted.
Immediately strain the custard through a fine-mesh sieve into a medium bowl. Whisk in the vanilla extract. Cover the surface of the custard with plastic wrap, and let cool to room temperature, then refrigerate for two hours, or until well chilled.
Just before assembling the cake, transfer the custard filling to the bowl of an electric mixer. Add 1/4 cup heavy cream and using the whisk attachment, beat the mixture at high speed until it is light and forms soft peaks, about 1 minute.
2 cups whole milk1/2 vanilla bean, split lengthwise, seeds scraped out6 egg yolks2/3 cup granulated sugar1/4 cup cornstarch1 tablespoon unsalted butter
CUSTARD:2 cups half and half6 large egg yolks½ cup (3.5 oz) granulated sugarpinch of table salt¼ cup cornstarch4 TB cold salted butter, cut into pieces1½ tsp pure vanilla extract
SPONGE CAKE:1½ cups (7.5 oz) all purpose flour1½ tsp baking powder¾ tsp table salt¾ cup whole milk6 TB salted butter1½ tsp pure vanilla extract3 large eggs1½ cups granulated sugar
GANACHE:½ cup heavy cream2 TB light corn syrup4 oz high quality bittersweet chocolate, chopped
CUSTARD: Heat half and half in a saucepan over medium heat until simmering. Meanwhile, whisk yolks, sugar, and salt in a bowl until smooth. Add flour to yolk mixture and whisk until combined. Remove half and half from heat and – whisking constantly – very slowly add ½ cup of half and half to the yolk mixture, to temper. Whisking constantly, return tempered yolk mixture to the remaining half and half in the saucepan.Return saucepan to medium heat and cook, whisking constantly, until it thickens, 1 min. Reduce to med-low and keep simmering, whisking constantly for 8 minutes. It will slowly go from pale yellow to a deep yellow and become thicker. Increase heat to medium and cook, whisking vidorously, until bubbles burst on surface, 1-2 min. Remove from heat and whisk in butter and vanilla until melted. It should be pudding-like, thick, and smooth (not clumpy.) Cover and chill at least 2 hours or overnight.SPONGE CAKE: Preheat oven to 325F with rack on middle position. Grease two 9-inch round cake pans and line with parchment over the grease. In a bowl, whisk flour, baking powder, and salt. In a saucepan, heat milk and butter over low heat until butter melts. Remove from heat, add vanilla, and cover to keep warm.In a stand mixer fitted with whisk attachment, whip the eggs and sugar at high speed until light and airy, 5 min. Add hot milk mixture and whisk by hand until combined. Add dry ingredients and whisk just until incorporated; don’t overmix.Quickly divide batter evenly between the two prepared pans. Bake until tops are golden brown and toothpick inserted in center comes out with small tender crumbs attached, about 20-27 min.Transfer cakes to wire rack and cool completely in pan at room temp. Run thin sharp knife around edge of pans and invert cakes onto rack. You might need to give the pans a good slap on the back. Slowly and gently peel off the parchment paper.Place one round cake on a serving plate, top side up. Stir chilled custard briefly and spread onto cake evenly. Place second round cake, bottom side up, on top of the custard. Cover and chill while you make the ganache.GANACHE: In a small saucepan over medium heat, bring heavy cream and corn syrup to simmer. Remove from heat and add chocolate chunks. Whisk until smooth. Let stand, whisking occasionally, until slightly thickened, 5-10 min. Whisk again and pour onto top of cake, using ruber spatula to spread evenly and letting it drip slowly down the sides. Cover and chill cake at least 3 hours before slicing. A fully chilled cake will be easier to slice.
For The Vanilla Custard Filling: