Choose the right mug or ramekin: Use a sturdy, oven-safe 10–12 ounce mug or a 6–8 ounce ramekin. Make sure it fits easily in your air fryer basket with room around it for airflow.
Preheat the air fryer: Set it to 350°F (175°C) for about 3 minutes.
Preheating helps the cake rise evenly and cook on time.
Mix dry ingredients: In your mug, whisk together flour, granulated sugar, brown sugar, cocoa powder, baking powder, and a pinch of salt until there are no streaks.
Add wet ingredients: Pour in milk, oil, and vanilla. Stir until smooth and well combined, scraping the bottom and sides of the mug. The batter should be thick but pourable.
Stir in extras: Fold in chocolate chips or your chosen add-ins.
For peanut butter, dollop it in the center and gently swirl for a molten pocket.
Air fry: Place the mug in the basket. Cook at 350°F (175°C) for 8–10 minutes. Start checking at 7 minutes.
The top should look set and spring back lightly when touched.
Check doneness: Insert a toothpick in the center. For a fudgier texture, a few moist crumbs are fine; for a cakier finish, it should come out mostly clean.
Rest briefly: Let it sit for 2 minutes. It continues to set and cools to a comfortable eating temperature.
Top and serve: Add a scoop of ice cream, whipped cream, berries, or a dusting of cocoa.
Enjoy warm.