Sunken Chocolate Cakes With Coffee Ice Cream

Preheat oven to 350°F Lightly butter 4 cups in a jumbo nonstick muffin pan, leaving the 2 center cups empty. Coat lightly with sugar, and set aside. Place butter and chocolate in a heat-proof bowl; set over a pan of simmering water. Stir occasionally, until melted and thoroughly combined. Remove from heat; set aside.
Combine the 4 egg yolks with 2 tablespoons sugar, and whisk until the mixture is pale yellow and thick. Stir in the melted chocolate-and-butter mixture.
Whisk egg whites until soft peaks form, add remaining 2 tablespoons sugar, and whisk until stiff and shiny but not dry. Fold into chocolate mixture. Divide batter among prepared muffin cups, and bake until set and slightly springy to the touch, about 25 minutes. Remove from oven, and transfer to a wire rack. Allow to cool for 15 minutes in pan; carefully run a knife around edges of cakes, and unmold. Serve each with a scoop of coffee ice cream.