Double Chocolate Layer Cake

Preheat oven to 300°F and grease two 10×2-inch round cake pans. Line bottoms with parchment paper.

Place chopped chocolate in a large bowl and pour hot coffee over it. Let sit for 4 to 5 minutes, then whisk until smooth.

Whisk in sugar, salt, oil, buttermilk, and vanilla until combined. Whisk in eggs, one at a time.

Sift flour, cocoa, baking soda, and baking powder into the bowl and whisk until smooth.

Divide batter between two pans and bake in the middle of the oven until a toothpick inserted in the center comes out clean, about 1 hour to 1 hour and 10 minutes.

Cool layers in pans for 5 to 10 minutes, then invert onto racks and cool completely.

For the frosting, finely chop chocolate. Bring cream, sugar, and corn syrup to a boil over moderately low heat, whisking until sugar is dissolved.

Remove from heat, add chocolate, and whisk until melted. Add butter and whisk until smooth.

Cool frosting until spreadable, stirring occasionally. Spread frosting between cake layers and over top and sides.

Cake layers can be made a day ahead and kept at room temperature, wrapped well in plastic wrap.