Step 1

Combine ripe banana, brown sugar, white sugar, salt, baking powder, baking soda, melted butter, milk, and vanilla in a mixing bowl; use a potato masher to mash the mixture into a smooth puree. Add flour and mix until just combined. Stir in walnuts and chocolate chips until evenly mixed.

Step 2

Transfer batter evenly into two lightly buttered coffee mugs or cups. Tap a few times on a towel to settle everything down and ensure there are no air pockets.

Step 3

Microwave cups, one at a time, until a toothpick comes out clean, about 1 minute.

Step 4

Let cool before serving.

Step 5

Optional: Garnish each with banana slices and dust with sugar. Brulee the tops with a blowtorch.