• For the Devil’s Food Cake:
• Preheat your oven to 350°F (175°C). Grease two 9-inch round baking pans with non-stick baking spray. Line the bottoms of the pans with parchment paper circles, then spray the parchment with non-stick spray as well. Set aside. In a large bowl, sift together the flour, cocoa powder, baking soda, baking powder, and salt. Set this mixture aside.
• In the bowl of a stand mixer fitted with the paddle attachment, or using a handheld mixer in a large bowl, beat the butter on medium speed until smooth, about 1 minute. Gradually add both sugars, one at a time, beating well after each addition until fully incorporated. Increase the mixer speed to high and beat the mixture until light and fluffy, about 4 minutes. Occasionally stop to scrape down the sides and bottom of the bowl to ensure everything is evenly mixed.
• Add the eggs and egg yolks one at a time, beating well after each and scraping the bowl as needed. Mix in the vanilla extract until combined. In a spouted measuring cup, combine the vegetable oil and sour cream.
• On the lowest speed, add the flour mixture in three parts, alternating with the sour cream mixture in two parts, mixing just until combined. Be careful not to overmix; the batter should still show a few streaks of dry ingredients when you stop.
• Pour in the hot coffee and let the batter rest, undisturbed, for 30 seconds. Then gently fold with a rubber spatula until the batter is evenly combined.
• Divide the batter evenly between the prepared pans (about 850 grams per pan), smoothing the tops with a spatula. Bake for 38 to 45 minutes or until a toothpick inserted in the center comes out clean or with a few moist crumbs.
• Place the pans on a wire rack and cool for 20 minutes. Then invert the cakes onto the rack and allow them to cool completely, about 1 hour.

For the Chocolate Frosting:

• Finely chop the chocolate with a large chef’s knife and place it in the bowl of a stand mixer fitted with the whisk attachment. In a small saucepan, heat the heavy cream and corn syrup over medium-high heat until it almost reaches a rolling boil. Remove from heat and pour the hot mixture over the chopped chocolate.
• Let it sit undisturbed for 2 minutes, then gently stir with a rubber spatula or metal spoon until the chocolate is fully melted and the mixture is smooth and glossy. Stir in the vanilla extract.
• With the mixer on medium speed, add the softened butter one tablespoon at a time, beating well after each addition before adding more. Stir in the salt.
• Refrigerate the frosting loosely covered for about 1 hour, or until firm enough to spread. The frosting can be made up to 24 hours in advance and stored in the refrigerator; bring it to room temperature before using.

Assembly:

• Using a long serrated knife, trim the domed tops off the cake layers to create smooth, even surfaces. Slice each cake layer in half horizontally to make 4 even layers total. Set aside any cake scraps for decoration later.
• Place one cake layer on a serving plate or cake stand. Spread about ½ cup of frosting evenly over the layer. Top with the next cake layer and repeat until all layers are stacked, finishing with the last layer on top. Spread the remaining frosting evenly over the top and sides of the cake.
• Crumble the reserved cake scraps into fine crumbs with your hands and gently press them around the sides of the cake. You may have extra crumbs—these can be discarded or enjoyed as a tasty snack!
• Allow the cake to set for 20 minutes before slicing. Serve immediately or store covered in the refrigerator for up to 5 days. Bring to room temperature before serving for best flavor and texture.