Instructions

• Preheat oven to 350°F. Line a baking sheet for the springform pan to sit on (optional for easier handling).
• In a medium bowl, stir together 2 cups chocolate wafer crumbs and 2 1/2 tablespoons sugar. Stir in 1/3 cup melted butter until evenly moistened.
• Transfer the crumb mixture to a 9-inch springform pan. Press the crumbs firmly and evenly onto the bottom and up the sides about 1 1/2 inches.
• Place the springform pan on the prepared baking sheet and bake the crust at 350°F for 10 minutes. Remove from the oven and let the crust cool while you prepare the filling.
• Put 2 cups (12 ounces) semisweet chocolate chips in a microwave-safe bowl. Heat in 20-second intervals, stirring after each interval, until the chocolate is completely smooth. Let the melted chocolate cool for a few minutes.
• In a medium bowl, whisk together 6 egg yolks, 1 3/4 cups heavy whipping cream, and 1 teaspoon vanilla extract until combined.
• With the egg mixture in a steady whisking motion, gradually pour the slightly cooled melted chocolate into the egg mixture to combine (this tempers the eggs). Whisk until the mixture is smooth and uniform.
• Pour the chocolate custard into the prepared crust. Bake at 350°F for 45 to 50 minutes, or until the center is almost set (it may still have a slight jiggle).
• Remove the pan from the oven and let the dessert cool on a wire rack for 10 minutes. Run a knife around the inside edge of the springform pan to loosen the dessert.
• Let the dessert cool to room temperature, then cover and refrigerate overnight.
• To make the buttercream, beat 1/2 cup softened butter in a bowl with an electric mixer until smooth.
• With the mixer on low, gradually add 3 cups confectioners’ sugar and 3 tablespoons unsweetened cocoa powder until mostly incorporated.
• Add 3 tablespoons milk and beat until smooth. If the frosting is too thick to pipe easily, add up to 1 additional tablespoon milk (up to 4 tablespoons total) until you reach a piping consistency that holds its shape but can be squeezed from a piping bag.
• If desired, release the springform pan sides and transfer the chilled dessert to a serving plate. Fit a pastry bag with a large star tip, fill with the buttercream, and pipe stars all over the top of the chilled dessert.