¼ cup all-purpose flour
½ teaspoon baking powder
4 tablespoons unsalted butter, cut into 4 pieces
3 tablespoons bittersweet or semisweet chocolate chips
2 large eggs
¼ cup sugar
2 tablespoons cocoa powder
1 teaspoon vanilla extract
⅛ teaspoon salt
gather cooking equipment
2 bowls
Whisk
2 coffee mugs (11 ounces each or larger, microwave-safe)
Oven mitts
In small bowl, whisk together flour and baking powder.
In medium microwave-safe bowl, combine butter and chocolate chips. Heat in microwave at 50 percent power for 1 minute. Stop microwave and stir mixture with spoon. Heat in microwave at 50 percent power until melted, about 1 minute. Remove bowl from microwave.
Add eggs, sugar, cocoa, vanilla, and salt to chocolate mixture and whisk until smooth.
Add flour mixture and whisk until smooth. Use spoon to divide batter evenly between 2 coffee mugs.
Place mugs on opposite sides of microwave turntable. Cook in microwave at 50 percent power for 1 minute. Stop microwave and use spoon to stir batter in each mug, making sure to reach bottom of mug.
Cook in microwave at 50 percent power for 1 minute (batter will rise to just below rim of mug and cake should look slightly wet around edges—if top still looks very wet, cook in microwave at 50 percent power for another 15 to 30 seconds).
Use oven mitts to remove mugs from microwave and let cool for 5 minutes. Serve warm.