Preparation Line 12-cup muffin pan with muffin papers. Combine chocolate and butter in heavy small saucepan; stir over medium-low heat until melted and smooth, about 1 minute. Remove saucepan from heat. Using electric mixer, beat sugar, eggs, egg yolks, and liqueur in large bowl until thick ribbon falls when beaters are lifted, about 5 minutes. Sift flour over; using rubber spatula, gently fold in flour. Fold in chocolate mixture. Divide batter among muffin papers. Cover and chill until cold and firm, at least 25 minutes. (Can be made 1 day ahead. Keep chilled.) Preheat oven to 400°F. Bake cupcakes in papers on baking sheet until tops are puffed and cracked and tester inserted into center comes out with moist batter attached, about 7 minutes. Serve cupcakes with whipped cream.
Preparation Line 12-cup muffin pan with muffin papers. Combine chocolate and butter in heavy small saucepan; stir over medium-low heat until melted and smooth, about 1 minute. Remove saucepan from heat. Using electric mixer, beat sugar, eggs, egg yolks, and liqueur in large bowl until thick ribbon falls when beaters are lifted, about 5 minutes. Sift flour over; using rubber spatula, gently fold in flour. Fold in chocolate mixture. Divide batter among muffin papers. Cover and chill until cold and firm, at least 25 minutes. (Can be made 1 day ahead. Keep chilled.) Preheat oven to 400°F. Bake cupcakes in papers on baking sheet until tops are puffed and cracked and tester inserted into center comes out with moist batter attached, about 7 minutes. Serve cupcakes with whipped cream.