01 - Preheat oven to 350°F. Grease and flour two 8-inch round cake pans.
02 - In a large bowl, beat together granulated sugar and softened butter until light and fluffy. Incorporate eggs one at a time, mixing well after each addition. Blend in vanilla extract.
03 - In a separate bowl, whisk all-purpose flour with baking powder and salt until evenly blended.
04 - Gradually add dry mixture to the wet ingredients, alternating with whole milk; begin and finish with flour. Stir gently until just combined.
05 - Divide batter equally into the prepared pans. Bake for 22 to 25 minutes, or until a toothpick comes out clean when inserted in the center.
06 - Allow cakes to cool in pans for 10 minutes, then remove and transfer to wire racks to cool completely.
07 - In a medium saucepan, heat whole milk until just simmering. In a bowl, whisk together granulated sugar, cornstarch, salt, and egg yolks until smooth.
08 - Slowly pour heated milk into the egg mixture, whisking continuously. Return mixture to saucepan and cook over medium heat, stirring constantly, until thickened and bubbling. Remove from heat; stir in butter and vanilla extract.
09 - Transfer pastry cream to a bowl, cover with plastic wrap directly on the surface, and chill in the refrigerator until fully set, at least 1 hour.
10 - Place chopped semisweet chocolate and unsalted butter in a heatproof bowl. Heat heavy cream just to a simmer and pour over chocolate. After 1 minute, stir until the mixture is smooth and glossy.
11 - Set one cake layer on a serving plate. Evenly spread chilled pastry cream over the surface. Top with the second cake layer.
12 - Pour chocolate glaze over the assembled cake, letting it cascade down the sides. Allow glaze to set for a minimum of 30 minutes before slicing and serving.