Choose the right mug. Use a microwave-safe mug that holds at least 12 ounces. A wider mug helps the cake cook more evenly.

Add dry ingredients. Into the mug, add 1/4 cup all-purpose flour, 2 tablespoons granulated sugar, 1 tablespoon unsweetened cocoa powder, 1/4 teaspoon baking powder, and a tiny pinch of salt. Stir to combine fully.

Mix in wet ingredients. Add 3 tablespoons milk, 2 tablespoons neutral oil, and 1/4 teaspoon vanilla extract. Stir until the batter is smooth and no dry streaks remain. Scrape the bottom edges so everything is incorporated.

Customize (optional). Fold in 1 tablespoon chocolate chips or press a small spoonful of peanut butter into the center for a molten middle. Keep add-ins modest so the cake cooks properly.

Microwave carefully. Microwave on high for 45–60 seconds to start. The cake should rise and look set on top but still slightly glossy in the very center.

Check doneness. If it’s still noticeably wet, heat in 10–15 second bursts until done. Most microwaves land between 60–90 seconds total. Avoid overcooking; the cake will finish setting as it rests.

Rest briefly. Let the mug cake sit for 1 minute. This helps it firm up and keeps the crumb tender.

Top and enjoy. Add a scoop of ice cream, a drizzle of chocolate syrup, or a dusting of powdered sugar. Eat warm right from the mug.