Prep Time: 30 minutesCook Time: 35 minutesChill Time: 3 hoursTotal Time: 4 hours 5 minutesServings: 12 squaresCourse: DessertCuisine: AmericanIngredientsFor the Chocolate Cake2 cups all-purpose flour¾ cup unsweetened cocoa powder2 teaspoons baking powder1 teaspoon baking soda½ teaspoon salt2 large eggs1 cup granulated sugar½ cup brown sugar½ cup vegetable oil1 cup buttermilk1 teaspoon vanilla extract½ cup hot coffeeFor the Vanilla Cream Filling2 cups whole milk½ cup granulated sugar¼ cup cornstarch2 large egg yolks2 tablespoons butter1 teaspoon vanilla extract1 cup heavy whipping cream, whippedFor the Chocolate Glaze1 cup semi-sweet chocolate chips½ cup heavy cream2 tablespoons butterInstructionsMake the Chocolate CakePreheat the oven to 350°F (175°C). Grease a 9x13-inch baking pan and line with parchment paper if desired.Whisk together the flour, cocoa powder, baking powder, baking soda, and salt.In another bowl, whisk the eggs, granulated sugar, brown sugar, oil, buttermilk, and vanilla.Gradually add the dry ingredients and mix just until combined.Slowly stir in the hot coffee. The batter will be fairly thin.Pour into the prepared pan and bake for 30–35 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.Cool completely.Make the Vanilla Cream FillingWarm the milk in a saucepan over medium-low heat.In a bowl, whisk together the sugar, cornstarch, and egg yolks.Slowly whisk some warm milk into the egg mixture, then return everything to the saucepan.Cook over medium-low heat, stirring constantly, until thick and creamy.Remove from heat and stir in the butter and vanilla.Cool completely, then gently fold in the whipped heavy cream.Spread the filling evenly over the cooled chocolate cake.Make the Chocolate GlazePlace the chocolate chips in a heatproof bowl.Heat the heavy cream until hot but not boiling.Pour the cream over the chocolate and let it sit for 2 minutes.Stir until smooth, then mix in the butter.Let the glaze cool slightly before spreading it evenly over the cream layer.Chill and ServeRefrigerate for at least 3 hours, or preferably overnight, until the layers are firm. Cut into 12 squares with a sharp knife, wiping the blade clean between cuts.TipsDon't add the cream filling until the cake is completely cool.Avoid overbaking to keep the chocolate cake moist.Hot water can replace the coffee if preferred.Chill thoroughly for clean, bakery-style slices.Keep leftovers covered in the refrigerator for up to 3–4 days.