To make the frosting: Put the chocolate in a large heatproof bowl. In a small saucepan, bring the cream to a boil. Pour the cream over the chocolate, move the bowl gently to let the cream settle. Set the mixture aside until softened, about 4 minutes. Whisk until smooth. Cover the surface of the frosting with plastic wrap. Set aside and let set up at room temperature, about 2 hours.
To make the cake: Set a rack in the middle of the oven and preheat to 350 degrees F. Lightly butter two 9-inch round cake pans and line the bottoms with a circle of parchment or wax paper.
In a medium bowl, whisk together the flour, baking soda, baking powder, and salt. Set aside.
In a standing mixer fitted with the paddle attachment, beat the butter at medium speed until smooth, about 2 minutes. Increase the speed to medium-high and slowly add the sugar. Continue beating until light and smooth, about 4 minutes. Turn the mixer off and scrape down the sides of the bowl with a rubber spatula. Add the cocoa powder and vanilla and beat at medium speed for 1 minute more. (Stop the machine and scrape down the sides of the bowl again, if needed.) With the mixer running at medium-low speed, add the eggs, one at a time, beating for 1 minute between each addition. Scrape down the sides of the bowl.
With the mixer at low speed, add the flour mixture, about a 1/4 cup at a time. Carefully pour the hot liquid into the batter. Remove the bowl from the mixer and, using a large rubber spatula, finish combining the batter until smooth. Divide the batter evenly between the prepared pans. Lightly drop each pan onto the counter to settle the batter.
Set the pans on the middle rack in the oven. Bake until the cakes begin to pull away from the sides of the pans and the center springs back when touched lightly, about 30 to 35 minutes.
Cool the cakes, in the pans, on a rack for 10 minutes. Turn the cake layers out of the pans and cool on the rack. (If not assembling the cake right away, wrap the layers in plastic wrap and store at room temperature for up to 1 day, or freeze for up to 2 months.)
Assemble the Devil's Food Cake. Place 1 cake layer upside-down on a cake stand or flat plate. Scoop about 1/3 of the icing onto the center of the layer. Using a large, offset spatula, spread the icing evenly over the layer to the edges. Place the other cake layer, rounded-side up, on top. Evenly spread half of the remaining icing over the top, spreading any excess icing down the sides. Spread the remaining icing around the sides of the cake. Use the tip of the offset spatula to make a swirling pattern in the icing. Serve. Store under a cake dome or loosely wrapped with plastic, at room temperature, for up to 2 days.