Heat oven to 350°F. Coat two 9 x 2-inch round cake pans with cooking spray. Line bottoms with waxed paper; coat paper with spray.
In small saucepan, melt chocolate with coffee over medium heat, stirring with whisk until smooth. Let cool to room temperature (to speed cooling, refrigerate chocolate mixture 10 to 15 minutes; dont let harden.)
In large bowl, mix flour, cocoa, baking soda, baking powder and salt.
In large bowl, beat butter, sugar and vanilla until creamy, 2 minutes. Beat in eggs, one at a time. Beat in chocolate mixture. On low speed, beat in flour mixture alternately with buttermilk, ending with flour; beat 1 minute. Divide between pans, 4 cups for each pan.
Bake in 350°F oven until toothpick tests clean, 40 to 45 minutes. Cool cakes in pans 10 minutes. Loosen edges; invert on racks. Remove paper; let cool.
Microwave chocolate in microwave-safe bowl on 100 percent power 1 minute; stir. Microwave 30 seconds; stir until smooth. In bowl, beat butter and salt until creamy, 2 minutes. On low, gradually beat in sugar until smooth, then melted chocolate. On medium speed, beat in cream until fluffy, 1 minute.
Place one cake layer on platter. Spread top with 1-1/2 cups frosting. Place second cake layer on top. Use remaining frosting to cover sides and top of cake. Serve or refrigerate. Let refrigerated cake stand (for frosting to soften) at room temperature at least 1 hour.