3 ounces of good semisweet chocolate
1 ½ 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 teaspoons baking soda
3/4 teaspoon baking powder
1 1/4 teaspoons salt
3 large eggs
3/4 cup melted butter
1 1/2 cups buttermilk
3/4 teaspoon vanilla
2 large egg whites
1/2 cup sugar
1/4 cup light corn syrup
2 tablespoons water
1 1/2 teaspoons pure vanilla extract
Preheat oven to 300°F. and grease pans. Line bottoms with wax paper.
Finely chop chocolate and in a bowl combine with hot coffee. Let mixture stand, stirring occasionally, until chocolate is melted and mixture is smooth.
Into a large bowl sift together sugar, flour, cocoa powder, baking soda, baking powder, and salt.
In another large bowl with an electric mixer beat eggs until thickened slightly and lemon colored (about 3 minutes with a standing mixer or 5 minutes with a hand-held mixer). Slowly add butter, buttermilk, vanilla, and melted chocolate mixture to eggs, beating until combined well.
Add sugar mixture and beat on medium speed until just combined well.
Divide batter between pans and bake in middle of oven until a tester inserted in center comes out clean, 1 hour to 1 hour and 10 minutes.
Cool completely in pan. Run a thin knife around edges of pans and invert layers onto racks. Carefully remove wax paper and cool completely.
While cooling, combine frosting ingredients with a pinch of salt in a metal bowl set over a saucepan of simmering water and beat with a handheld electric mixer at high speed until frosting is thick and fluffy, 6 to 7 minutes. Remove bowl from heat and continue to beat until slightly cooled. Use frosting the day it is made.
Slice cakes in half and fills with marshmallow frosting.
I got the recipe here.