Prepare a double-boiler: place a large heat-proof bowl over pan, being sure water does not touch bowl, and add chocolate and butter to bowl. Once chocolate is completely melted, stir in the butter one piece at a time until fully incorporated. Keep scraping bowl with a rubber spatula so chocolate does not scorch. Remove bowl from pan and set aside. In same double-boiler: Place large heat-proof bowl and whisk together yolks, coffee and vanilla. While whisking, slowly add in sugar and whisk until thick. Pour mixture into a stand mixer and whisk until cool. Meanwhile, in another kitchen aid or by hand in a chilled bowl, lift the cream into soft peaks. Fold cream into cooled cooked eggs and cooled chocolate. Use for the below applications as it will set when cooled. Store in fridge.