This microwave brownie cake in a mug is made with flour, cocoa powder, sugar, an egg, milk, oil, a little baking powder, and chocolate chips, stirred together in one mug and cooked in about 90 seconds.

It’s somewhere between a brownie and a chocolate cake, soft and springy with a gooey chocolate center.

It’s great for a quick dessert after dinner, a single-serving birthday treat, or a cozy snack on a cold night. There’s an air fryer version too, and if you’re into mug desserts, this cinnamon roll mug cake is another favorite.

If you love quick chocolate desserts, these are worth bookmarking too:

Microwave Brownie Cake in a Mug (Plus Air Fryer Version)

Ingredients You’ll Need

The egg and baking powder are what make this cakier than a classic mug brownie. Use a neutral oil, since it keeps the crumb softer than butter once it cools.

Ingredients

1 large egg
3 tablespoons milk
2 tablespoons vegetable or canola oil
1/4 teaspoon vanilla extract
4 tablespoons all-purpose flour
3 tablespoons granulated sugar
2 tablespoons unsweetened cocoa powder
1/4 teaspoon baking powder
1 pinch salt
2 tablespoons semi-sweet chocolate chips, divided

Directions

Grab a large microwave-safe mug, at least 14 ounces, since this one rises more than a regular brownie.
Lightly grease the inside with a little oil or cooking spray.
For the air fryer version, grease an oven-safe ramekin or mug instead.
Crack the egg into the mug and beat it with a fork for about 20 seconds until the yolk and white are fully mixed.
Add the milk, oil, and vanilla and whisk until smooth.
Any streaks of egg white will cook into rubbery spots, so beat it well.
A small whisk works even better than a fork if you have one.
Add the flour, sugar, cocoa powder, baking powder, and salt.
Stir until the batter is smooth and no dry flour remains, scraping the bottom and corners.
The batter should be glossy and about as thick as regular cake batter.
Stir in 1 tablespoon of the chocolate chips.
Press the remaining chips into the top of the batter, right in the center.
Those melt into a little pool of chocolate in the middle, which is the best part.
Wipe the rim of the mug clean before cooking so stray batter doesn’t overcook and stick.
Microwave on high for 70 to 90 seconds.
Watch it through the door: it will puff up well above the batter line, then settle slightly.
It’s ready when the top looks dry and springs back when lightly touched (a slightly glossy spot in the center is fine).
Stop and check at 70 seconds the first time, since overcooking happens fast.
For the air fryer, mix the batter in a small bowl and pour it into the greased ramekin, filling it no more than two thirds full.
Air fry at 330°F (165°C) for 12 to 14 minutes, until a toothpick inserted near the edge comes out clean and the center has a few moist crumbs.
If the top browns too quickly, lay a small piece of foil over it for the last few minutes.
Let the brownie cake rest for 2 minutes before digging in.
It sinks a little as it cools (totally normal for mug cakes).
The steam escaping from the top is what makes it deflate, and it doesn’t affect the texture.
Run a knife around the edge if you want to flip it out onto a plate.
Top with whipped cream or ice cream and enjoy!

Important Recipe Notes

Beat the egg thoroughly. Mug cakes use a whole egg in a small amount of batter, so any unmixed white turns spongy. Twenty seconds of beating fixes that.
Use a big enough mug. This batter rises a lot in the microwave. A small mug will overflow, so use at least 14 ounces or set it on a plate just in case.
Start with less time. Microwaves vary widely. Start at 70 seconds and add 10 seconds at a time until the top springs back.
Keep the air fryer moderate. At 330°F the cake rises evenly and stays moist. Hotter air fryers can crack and dry out the top before the middle sets.

Brownie or cake texture. For something fudgier, use just the egg yolk instead of a whole egg. For something lighter and cakier, add another 1/4 teaspoon of baking powder.
Don’t let it sit too long. Mug cakes are best within 10 minutes of cooking. They firm up quickly as they cool, which is a bit of a downside if you’re making several at once.
Make two at once. Mix two mugs, but microwave them one at a time. Cooking both together makes timing unpredictable.
Measure with real spoons. With such a small batch, an extra spoonful of flour or sugar changes the texture a lot. Use measuring spoons and level them off with a knife instead of eyeballing it.
Storage. Cover and refrigerate leftovers for up to 2 days. Warm in the microwave for 10 to 15 seconds before eating.

How to Serve, Store & Customize This Recipe

Serving:

Serve the brownie cake warm in the mug with a scoop of vanilla ice cream or a spoonful of whipped cream.

Fresh strawberries or a drizzle of chocolate sauce are easy upgrades. For a birthday treat, top it with sprinkles and a single candle.

Storage:

It’s best eaten fresh, but you can cover the mug with plastic wrap and refrigerate it for up to 2 days. A quick 10 to 15 seconds in the microwave softens it again.

For quick desserts, pre-mix the dry ingredients in small jars and keep them in the pantry.

Customization:

Add 1 tablespoon of peanut butter in the center before cooking for a peanut butter cup version.

A pinch of cinnamon or chili powder gives it a Mexican chocolate twist. Swap the chocolate chips for white chocolate or mint chips if you want something different.