Step 1: Make the Pastry Cream Heat 2 cups whole milk until hot. In a separate bowl, whisk 6 egg yolks (room temperature) and ⅔ cup sugar until light and thick. Sift in ¼ cup corn starch, then gradually whisk in the hot milk. Pour the mixture back into the pan, and cook over medium-high heat, whisking constantly, until it thickens and boils. Stir in 1 tablespoon butter, let it cool slightly, cover, and chill in the refrigerator.

Step 2: Preheat and Prep the Pan Preheat your oven to 350°F and prepare an 8-inch cake pan by greasing, flouring, and lining it with parchment paper. In a bowl, whisk together 1 cup all-purpose flour plus 2 tablespoons, 1¼ teaspoons baking powder, and ¼ teaspoon kosher salt to ensure even leavening.

Step 3: Make the Cake Batter Beat 2 large eggs (room temperature) and 1 cup cane sugar on medium speed until pale and fluffy, about 4 minutes. In a saucepan, heat ½ cup whole milk and 5 tablespoons unsalted butter until the butter melts and the milk steams. On low speed, mix the flour mixture into the eggs just until combined. Stir 2 teaspoons vanilla extract into the hot milk mixture, then slowly add it to the batter, mixing until smooth. Pour the batter into the prepared pan for even baking.

Step 4: Bake the Cake Bake for about 33 minutes, or until a toothpick inserted in the center comes out clean. Let the cake cool completely on a wire rack to prevent it from becoming soggy when assembled.

Step 5: Assemble the Cake Slice the cooled cake horizontally in half. Spread the chilled pastry cream evenly over the bottom layer, leaving a 1-inch border. Place the top layer on and chill for at least 2 hours or overnight to let the flavors meld.

Step 6: Make the Ganache and Finish Heat ¼ cup heavy whipping cream until steaming, then pour it over 4 ounces chopped bittersweet chocolate. Let it sit for 5 minutes, then stir until smooth. Pour the ganache over the chilled cake and spread it evenly to the edges for a glossy finish.