Follow these simple, step-by-step instructions to ensure a perfectly cooked, fluffy, and delicious mug cake every single time. The process is designed to be quick, easy, and virtually foolproof.

Step 1: Prepare the Banana
Find a large, microwave-safe mug (at least 12-14 ounces in capacity is ideal to prevent overflowing). Peel your very ripe banana and place it directly into the mug. Using a fork, press and mash the banana against the bottom and sides of the mug until it becomes a smooth, mostly lump-free puree. The smoother the banana, the better it will incorporate into the batter, ensuring consistent flavor and texture throughout the cake.

Step 2: Add Wet Ingredients
To the mashed banana in the mug, add the egg, milk, vegetable oil, and vanilla extract. Use the same fork to whisk these wet ingredients together vigorously. Continue whisking until the egg is fully broken up and everything is combined into a smooth, homogenous liquid. This step is crucial for creating the moist foundation of your cake.

Step 3: Incorporate Dry Ingredients
Now, add the dry ingredients directly on top of the wet mixture in the mug. Sprinkle in the all-purpose flour, granulated sugar, baking powder, and the pinch of salt. Using your fork, gently stir everything together. Start slowly to avoid a puff of flour escaping the mug. Mix only until you no longer see dry streaks of flour. It’s very important not to overmix at this stage. A few small lumps in the batter are perfectly fine; overmixing can develop the gluten in the flour, leading to a tough or rubbery cake.

Step 4: Fold in the Chocolate Chips
Sprinkle in the chocolate chips, reserving a few to place on top if you wish. Gently fold them into the batter with just a couple of stirs. This ensures they are evenly distributed throughout the cake, so you get a bit of chocolatey goodness in every bite. Placing a few extra on top before cooking guarantees a beautiful, molten-topped presentation.

Step 5: Microwave to Perfection
Wipe any batter drips from the rim of the mug for a clean look. Place the mug in the center of your microwave. Cook on high power for 90 seconds to 2 minutes and 30 seconds. The exact cooking time will vary significantly depending on your microwave’s wattage (e.g., a 1200W microwave might only need 90 seconds, while a 700W one might need the full 2.5 minutes). Start by checking at the 90-second mark. The cake is done when the top looks set and dry, and it springs back lightly when you touch it. If it’s still wet in the center, microwave in additional 15-second intervals until it’s cooked through. Be careful not to overcook, as this is the primary cause of a dry or rubbery mug cake.

Step 6: Rest and Enjoy
Carefully remove the mug from the microwave—it will be very hot! Let the cake rest for at least 1-2 minutes before diving in. This resting period allows the cake to finish cooking with its residual heat and lets the molten center cool down just enough to avoid burning your mouth. The cake will also firm up slightly as it cools. Enjoy it straight from the mug with a spoon for the ultimate comforting dessert experience.