In a microwave-safe mug, sift together the flour, brown sugar, baking powder, ground ginger, ground cinnamon, ground nutmeg, and salt. Stir these dry ingredients together until fully blended.

Add the milk, vegetable oil, and vanilla extract to the dry mixture in the mug. Mix until the batter is smooth and free of lumps.

Place the mug in the microwave and cook on high for about 1 minute and 20 seconds. Avoid overcooking to maintain its moist texture.

Carefully remove the mug from the microwave and allow the cake to cool for a minute or two before serving. Add optional toppings if desired.