Ingredients
Method
- Choose your mug. Use a microwave-safe mug with a capacity of at least 12 ounces (350 ml). The batter rises significantly during cooking, and you need headroom to prevent overflow. Larger is better than smaller here.
- Melt the butter. Add the butter to your mug and microwave for about 20 seconds until fully melted. Let it cool for 30 seconds so it doesn't scramble the egg if you're using one.
- Combine the wet ingredients. Stir the mashed banana, brown sugar, milk, and vanilla extract into the melted butter. Mix thoroughly with a fork until smooth and the banana is completely incorporated. A few small lumps of banana are fine and add texture.
- Add the dry ingredients. Sprinkle the flour, baking powder, cinnamon, and salt over the wet mixture. Fold gently until no dry streaks remain — scrape the sides and bottom of the mug. Stop mixing the moment the batter is combined; over-mixing makes the cake tough.
- Fold in mix-ins. If using chocolate chips or nuts, fold them in now. For a particularly gooey result, reserve a few chips to scatter on top of the batter before microwaving.
- Microwave. Cook on high power for 60 to 90 seconds. Start checking at 60 seconds — the top should look set and spring back to a gentle touch, and the edges should pull slightly from the mug walls. The centre can look just slightly moist; it will finish cooking during the rest.
- Rest and serve. Let the mug cake sit for 1–2 minutes before eating. It is extremely hot straight from the microwave. Eat directly from the mug while warm, topped with anything from your optional toppings list.
Notes
Microwave wattages vary widely (600W to 1200W). If your microwave is powerful (1000W+), check at 60 seconds. If it is lower power, you may need up to 2 minutes. Add time in 10-second increments and check after each.