Mix flour, baking powder, and a pinch of salt in a large, microwave-safe mug.
Stir in oil, milk, 1 tbsp. honey, and vanilla until smooth.
Fold in chopped banana gently.
In a separate bowl, mix remaining 1 tbsp. honey, peanut butter, and a pinch of salt.
Place peanut butter mixture in the center of mug batter. Press it down slightly.
Microwave on high for 90 seconds. If still wet on top, cook in 15-second intervals.
If desired, run a knife around the mug and unmold onto a plate.
Top with chopped banana and honey drizzle if desired.
