You can buy this cake from 2 canadian sources: M&M or Save-on-Foods:
Basically it's 3 layers of marbled cake with a layer of dark chocolate mousse and white chocolate mousse in between, coated with ganache on the top. I took recipes from several sources to put this cake together. Success! While it's not as pretty as the commercial ones, everyone loved it and it tasted pretty damn close to the ones you buy.
Tuxedo Truffle Cake
3 cups Sifted all-purpose flour
1 tbsp Baking powder
1 tsp Baking soda
1/2 tsp Salt
1 cup Unsalted butter
2 cups sugar
1 1/4 cups Buttermilk
1 1/2 tsp vanilla extract
1/4 cup cocoa powder
4 oz. bittersweet chocolate
4 oz white chocolate
3 cups whipping/heavy cream
6 oz bittersweet chocolate
3/4 cup whipping/heavy cream
1. CAKE: Preheat oven to 350 degrees F. Line a 15x10" jelly roll pan with parchment paper and grease and flour it. Sift together the flour, baking powder, baking soda, and salt; set aside. In the bowl of a standing mixer, cream butter at medium speed until softened, 1 to 2 minutes. Gradually add sugar and vanilla, and continue until lightened, 3 to 4 minutes, scraping down sides once or twice. Gradually add eggs, beating after each addition until batter is no longer slick, stopping once or twice to scrape down the sides, about 5 minutes. Slowly add the sifted flour mixture, alternating with the buttermilk, a little of each at a time, at low speed, beginning and ending with the flour mixture. Scrape 2/3 of the batter into the prepared jelly roll pan. Add the cocoa to the remaining 1/3 batter, mix it in then drop by the tablespoonfuls onto the yellow batter. Marble with a knife. Bake for approx 30 minutes or until cake is done. Cool fully, overnight in the fridge is better/
2. MOUSSE: In two separate small bowls, place the finely chopped white and the bittersweet chocolate. Bring 3/4 cup cream to a boil then pour half over each of the chocolates to melt them. Stir the hot cream in well to ensure it is free of lumps and chocolate is fully melted. Set aside for 10 minutes until slightly cooled. Whip 2 1/4 cups of the cream until soft peaks form. Divide the whipped cream into two equal portions and fold the chocolate into each. You should now have one bowl of white chocolate mousse and one bowl of dark chocolate mousse. Store in fridge.
3. ASSEMBLY: With the long end of the pan facing you, cut your baked cake into thirds, creating 3 layers. Spread the dark mousse over the first layer and freeze for 15-30 minutes to set. Top with next layer of cake then white mousse. Freeze again. Finally, put the last cake layer on top and store in freezer while you make the ganache
4. GANACHE: Place the finely chopped bittersweet chocolate in a bowl. Bring the cream to a boil then pour over the chocolate. Stir to incorporate and melt chocolate. Spread over the top of the cake. Tada! A fancy and very tasty tuxedo cake.