Step 1: Prepare Your Mug

Choose a microwave-safe mug that holds at least 12 ounces. This is not optional — the batter rises significantly during cooking and a smaller mug will overflow. Lightly grease the inside with a little butter or cooking spray for easier cleanup.

Step 2: Mix the Dry Ingredients

Add the flour, granulated sugar, cocoa powder, baking powder, and salt directly into the mug. Whisk thoroughly with a fork, breaking up any cocoa lumps completely. Undissolved lumps will create bitter, uneven pockets in the finished cake.

Step 3: Add the Wet Ingredients

Pour in the milk, oil or melted butter, and vanilla extract. Stir vigorously for about 30 seconds until the batter is completely smooth with no flour streaks visible. The mixture should be thick but pourable.

Step 4: Build the Pudding Layer

In a small bowl or directly on top of the batter, mix the brown sugar and remaining tablespoon of cocoa powder together. Sprinkle this mixture evenly over the surface of the batter — do not stir it in. Then carefully pour the hot water over the top. Resist the urge to mix. This layering is the technique that creates the self-saucing pudding at the bottom of the mug as it cooks.

Step 5: Microwave

Microwave on high for 1 minute 30 seconds to 2 minutes, depending on your microwave's wattage. The top of the cake should look set but the center should still have a slight jiggle — that is the pudding sauce forming underneath. If you prefer a firmer texture throughout, add 15-second intervals and check between each. Do not overcook; it is the most common mistake with this recipe.

Step 6: Rest and Serve

 

Let the mug rest for 1 minute after cooking. This allows the pudding sauce to settle and thicken at the bottom and the cake to reach its ideal consistency. Add toppings and serve immediately, eating directly from the mug.