4 tablespoons unsalted butter
1 ounce bittersweet chocolate, chopped, plus 1 ounce broken into 4 equal pieces
1/4 cup (1 3/4 ounces) sugar
2 large eggs
2 tablespoons unsweetened cocoa powder
1 teaspoon vanilla extract
1/4 teaspoon salt
1/4 cup (1 1/4 ounces) all-purpose flour
1/2 teaspoon baking powder
WHY THIS RECIPE WORKS: These individual chocolate cakes are cooked in coffee mugs in the microwave for a nearly instant dessert. To keep our cakes from overflowing, we had to supplement bittersweet chocolate with cocoa powder; cocoa powder has less fat, which produces less steam, thus less chance of an overflow. Microwaving the cakes on 50 percent power was the key to cooking them gently, helping create a light, tender crumb, and stirring the batter halfway through ensured even cooking. Finally, a few chunks of bittersweet chocolate added to each cake created a gooey, molten center.
1. Microwave butter and chopped chocolate in large bowl, stirring often, until melted, about 1 minute. Whisk sugar, eggs, cocoa, vanilla, and salt into chocolate mixture until smooth. In separate bowl, combine flour and baking powder. Whisk flour mixture into chocolate mixture until combined. Divide batter evenly between 2 (11-ounce) coffee mugs.
2. Place mugs on opposite sides of microwave turntable. Microwave at 50 percent power for 45 seconds. Stir batter and microwave at 50 percent power for 45 seconds (batter will rise to just below rim of mug). Press 2 chocolate pieces into center of each cake until chocolate is flush with top of cake. Microwave at 50 percent power for 35 seconds (cake should be slightly wet around edges of mug and somewhat drier toward center). Let cakes rest for 2 minutes. Serve.