15 ounces semi-sweet chocolate, finely chopped
1 1/2 cups heavy cream
2 cups all-purpose unbleached flour
1 1/2 teaspoons baking soda
3/4 teaspoon baking powder
3/4 teaspoon salt
12 tablespoons unsalted butter, at room temperature, plus more for pans
2 cups plus 2 tablespoons sugar
3/4 cup non-alkalized cocoa powder (not Dutch-processed)
2 teaspoons pure vanilla extract
3 large eggs, at room temperature
1/4 cup milk
Raspberries, for garnish, optional
1. For frosting: Place chocolate in a large heatproof bowl. Bring cream to a boil in a small saucepan and immediately pour over chocolate. Set aside until chocolate softens, about 4 minutes. Stir until smooth. Cover surface of frosting with plastic wrap and let sit until room temperature, about 2 hours.
2. For cake: Preheat oven to 350F. Lightly butter two 9-inch round cake pans; line bottoms with parchment paper.
3. Whisk flour, baking soda, baking powder, and salt together in a medium bowl. Set aside. Beat butter using a mixer set at medium speed until smooth. Increase speed to medium-high and gradually add sugar. Beat until light and smooth, about 4 minutes. Scrape down bowl sides as needed. Add cocoa and vanilla, and beat at medium speed for 1 minute. Reduce speed to medium-low and add eggs, one at a time and beating for 1 minute between each addition.
4. Bring 1 1/2 cups water and milk to a boil in a saucepan. Remove from heat.
5. Beat flour mixture into batter 1/4 cup at a time using mixer set at low speed. Carefully pour hot milk mixture into batter. Stir using a rubber spatula until smooth. Evenly divide batter among prepared pans. Lightly tap pans on counter to distribute batter.
6. Bake on middle rack in oven until cakes begin to pull away from pan sides and center springs back when touched lightly, about 30 to 35 minutes. Cool cakes, in pans, on a rack for 10 minutes. Release from pans and cook completely on rack.
7. Ice cake, spreading 1/3 cup frosting between layers and remainder over top and sides. Garnish with raspberries.