For the brownies:
10 oz. semisweet or bittersweet chocolate, chopped
4 oz. unsweetened chocolate, chopped
16 tbsp. (1 cup) unsalted butter, cut into chunks
6 tbsp. cocoa powder
6 large eggs
2½ cups (17.5 oz.) sugar
1½ tbsp. vanilla extract
1 tsp. salt
2 cup (10 oz.) all-purpose flour
About 2 tbsp. Kahlua (or other coffee-flavored liqueur)
About 2 tbsp. Bailey’s Irish Cream
For the whipped cream:
1½ cups heavy cream
½ cup confectioners’ sugar
2 tbsp. plus 1 tsp. Kahlua
2 tbsp. plus 1 tsp. Bailey’s Irish Cream
Chocolate syrup, for drizzling
Place an oven rack in lower-middle position and preheat the oven to 350° F. Line the bottom of three 8-inch round cake pans with parchment paper. Lightly grease and flour the edges of the pans, shaking out the excess. Set aside. In a heatproof bowl set over a pan of barely simmering water, melt the chocolate and butter, stirring occasionally until smooth. Whisk in the cocoa powder until smooth. Set aside to cool.
In a medium bowl, combine the eggs, sugar, vanilla and salt; whisk until combined, about 15 seconds. Whisk in the warm chocolate mixture until incorporated. Then stir in the flour with a wooden spoon until just combined. Divide the batter evenly between the prepared pans and spread into even layers. Bake until slightly puffed and a toothpick inserted in the center comes out with a small amount of sticky crumbs clinging to it, 30-35 minutes.
Transfer the pans to a wire rack. Brush the warm brownie layers with Kahlua and Bailey’s. Allow it to soak in and repeat one more time. Let cool to room temperature, about 2 hours. Run a knife along the outside edge of the brownie layers and carefully turn them out of the pans. Remove the parchment paper.
When ready to serve, place a brownie layer on a cake board or cake platter. In an electric mixer fitted with the whisk attachment, combine the heavy cream and confectioners’ sugar. Whip on medium-high speed until medium-stiff peaks form. Blend in the Kahlua and Bailey’s until evenly incorporated. Spread about a third of the whipped cream in an even layer over the first brownie layer. Drizzle generously with chocolate syrup. Top with a second layer of brownie. Smooth half of the remaining cream over the top and drizzle with chocolate syrup. Place the final brownie layer on top, top with remaining whipped cream and drizzle with chocolate syrup. Slice and serve.