Preheat oven to 350°F (180°C). Generously butter 2 (9-inch) round cake pans. Line bottom of pans with parchment paper.

In the bowl of a stand mixer fitted with the paddle attachment, beat butter and sugar at medium speed until fluffy, about 4 minutes, stopping to scrape sides of bowl. Add eggs, one at a time, beating well after each addition. Beat in vanilla.

In a medium bowl, whisk together flour, baking powder, and salt. With mixer on low speed, add flour mixture to butter mixture in two additions alternately with milk, beginning and ending with flour mixture, beating until just combined after each addition. Scrape sides of bowl, and fold in any ingredients that are not fully incorporated. Divide batter between prepared pans (about 2 cups or 492 grams each), and spread evenly with an offset spatula.

Bake until a wooden pick inserted in center comes out clean, 18 to 20 minutes. Let cool completely in pans.

Remove cooled cake layers from pans. Place 1 cake layer on a cake plate, and spread Creamy Ricotta-Mascarpone Filling on top. Place remaining cake layer on filling. Pour half of Chocolate Ganache on top of cake, and using an offset spatula, spread and push ganache over top of cake and onto sides of cake and filling. Add remaining ganache in sparse areas, and spread, smooth, and texture as desired. Serve immediately while ganache is shiny and slightly warm. Cover and refrigerate for up to 3 days.