In a 12 oz. microwave safe mug, combine 2 Tablespoons milk , 4 Tablespoons pure pumpkin puree, ½ teaspoon vanilla extract, and 2 Tablespoons brown sugar.
Add ½ teaspoon cinnamon, ¼ teaspoon ginger, pinch allspice,4 Tablespoons all purpose flour, 1 teaspoon baking powder, and pinch of salt. (Can substitute with ¾ teaspoon pumpkin pie spice. Mix well.
Microwave on high power for 2 minutes. Sometimes the mug cake rises a little above the edge of the mug, it shrinks back down as it cools. It's never overflowed for me.
Optional: Add whipped cream and sprinkle some mini chocolate chips on top!
Notes
Best served fresh! You can make the batter ahead and refrigerate it before cooking if you wish. Just make sure to cook it for 2 minutes 30 seconds if microwaving straight from the fridge.