1/4 cup whole or 2% milk
1/4 cup all-purpose flour
1/4 teaspoon baking powder
1/4 cup Nutella
Place the milk, flour, and baking powder in a 12-ounce or larger microwave-safe mug and whisk until smooth. Add the Nutella and stir until the batter is well-blended with no lumps.
Microwave on high for 60 seconds, and then in 15-second bursts until the cake begins to pull away from the sides of the mug and the top looks set, dry, and springs back when gently touched, 30 to 60 seconds more. Serve immediately.