Chocolate cake with Nutella frosting

My sister's birthday was last week, and we had her over for a birthday dinner last night. I asked her what kind of cake she wanted me to make, and she said chocolate with hazelnuts. I didn't find a satisfactory recipe in my cookbooks, so I decided to adapt a double chocolate layer cake recipe that I found in Gourmet Today. To get the hazelnut flavor in there, I added Nutella to the chocolate frosting, and also used Nutella between the cake layers instead of frosting.

Let me tell you, this cake is incredible. Just incredible. It's rich, intensely chocolatey, and very moist, and the Nutella adds a nice flavor dimension. The frosting is a ganache, which was pretty easy to make and work with. This chocolate cake recipe is an absolute keeper, and popular opinion agrees with me - turns out it is one of the all-time highest rated recipes on Epicurious. You'll never need another chocolate cake recipe again after trying this one!

Chocolate cake with Nutella frosting 
Adapted from Gourmet Today
Serves 12-16

If you want to try the double chocolate version without Nutella, the original recipe can be found here.

Note: it has come to my attention that some people find that there is too much batter for 2 cake pans. I have made this cake multiple times and have not had this problem, but if you find that there is excess batter I can suggest two things: 1) split the batter among three cake pans, 2) use the excess batter to make cupcakes (make sure to check for doneness earlier if you do this). Hope this helps!

For cake layers:
3 ounces semisweet chocolate (no more than 60% cacao), finely chopped
1 1/2 cups hot brewed coffee
3 cups sugar
2 1/2 cups all-purpose flour
1 1/2 cups unsweetened cocoa powder (not Dutch-process)
2 tsp baking soda
3/4 tsp baking powder
1 1/4 tsp salt
3 large eggs
3/4 cups vegetable oil
1 1/2 cups well-shaken buttermilk
3/4 tsp vanilla extract

For frosting:
1 cup heavy cream
2 tbs sugar
2 tbs light corn syrup (I used dark, and it was fine)
12 ounces semisweet chocolate (no more than 60% cacao), finely chopped
1/2 stick (4 tbs) unsalted butter, cut into cubes and chilled
1/2 cup Nutella

Between cake layers: about 3/4 cup Nutella

Special equipment: two 9-by-2-inch or 10-by-2-inch round cake pans, parchment paper

Make cake layers:
Put a rack in the middle of the oven and preheat to 300 deg F. Grease cake pans, line bottoms with rounds of parchment paper, and grease parchment. Put chocolate in a bowl, and pour hot coffee over it. Let stand, stirring occasionally, until chocolate is melted and mixture is smooth. In a separate bowl, sift together sugar, flour, cocoa powder, baking soda, baking powder, and salt.

Beat eggs in a large bowl with an handheld electric mixer, or stand mixer with whisk attachment, at high speed until eggs are slightly thickened and pale, about 3 minutes if using a stand mixer. Reduce speed to medium and slowly add oil, then buttermilk, vanilla, and melted chocolate mixture. Beat until well combined, then add flour/sugar mixture and beat until well combined.

Divide batter between prepared cake pans and bake in preheated oven, until a wooden toothpick inserted in the center of the cakes comes out clean, about 1 hour and 10 minutes to 1 hour and 20 minutes. Cool cakes in the pans on a rack for 1 hour. Run a thin knife around the sides of the pans and then invert cakes onto racks. Remove parchment paper and cool cakes completely.

Make frosting:
Bring cream, sugar, and corn syrup to a boil in a 1 1/2-to-2-quart saucepan over moderate heat, whisking until sugar is dissolved. Remove pan from heat and then add chocolate. Whisk until chocolate is melted, then add butter and whisk until melted. Add Nutella and whisk until smooth. Cool frosting until spreadable (you might need to refrigerate it to get it to a spreadable consistency, depending on the chocolate that you used).

Assemble the cake:
Put 1 cake layer flat side down on a stand or plate, and spread top with about 3/4 cup Nutella. Top with second cake layer, flat side up. Frost top and sides of cake with chocolate-Nutella frosting (you will probably end up with some extra frosting, but it is always good to have some excess to do touch-ups if necessary).