Pin it Some nights you just need something sweet right now, not in thirty minutes. I threw this together one evening when I had nothing in the house but peanut butter and a rogue egg in the fridge. The microwave hummed, the mug puffed up like a little soufflé, and suddenly I had warm cake without turning on the oven. It's been my midnight answer ever since.
I made this for my sister once when she showed up stressed after a long shift. She stood in my kitchen, ate it straight from the mug with a spoon, and actually laughed. Sometimes the fastest dessert is the one that matters most.
Ingredients
- Creamy peanut butter: The backbone of the flavor, smooth types mix better than chunky here.
- Unsalted butter, melted: Adds moisture and helps the texture stay tender instead of rubbery.
- Large egg: Gives structure and lift, whisked in with a fork works perfectly.
- Milk: Any kind works, I use oat milk half the time and never notice a difference.
- Vanilla extract: Rounds out the sweetness and makes it smell like a real bakery.
- All-purpose flour: Just enough to hold it together without making it dense.
- Granulated sugar: Sweetens without overpowering the peanut butter.
- Baking powder: The magic that makes it puff up in the microwave.
- Pinch of salt: Balances everything and makes the peanut butter taste richer.
Instructions
- Mix the fats:
- In a large microwave-safe mug, stir together the peanut butter and melted butter until smooth and glossy. This creates the base that keeps everything moist.
- Add the wet ingredients:
- Crack in the egg, pour in the milk and vanilla, then whisk everything with a fork until no streaks remain. It should look like a loose batter.
- Fold in the dry ingredients:
- Add the flour, sugar, baking powder, and salt, stirring just until incorporated. A few small lumps are fine, overmixing makes it tough.
- Microwave it:
- Cook on high for 60 to 75 seconds, watching as it rises and sets in the center. Stop when the top looks dry but still soft.
- Cool and enjoy:
- Let it sit for a minute or two so you don't burn your tongue. Then eat it straight from the mug while it's still warm.
Pin it The first time I made this, I ate it standing at the counter with a spoon, still in my coat. It wasn't fancy, but it was exactly what I needed. That's the kind of recipe this is.
How to Know When Its Done
The top should look set and slightly dry, not wet or shiny. If you gently press the center with your finger, it should spring back. Microwaves vary, so start with 60 seconds and add 10-second bursts if needed. Better to undercook slightly than turn it into a hockey puck.
Best Toppings and Add-Ins
I love dropping a handful of chocolate chips into the batter before microwaving, they melt into pockets of fudge. A drizzle of honey or a scoop of vanilla ice cream on top turns it into something almost fancy. Sometimes I just eat it plain and it still feels like a treat.
Storage and Reheating
This is best eaten fresh and warm, but if you have leftovers, cover the mug and refrigerate for up to one day. Reheat in the microwave for 15 to 20 seconds. The texture won't be quite as fluffy, but it still tastes good.
- You can make the batter ahead and refrigerate it, then microwave when ready.
- Double the recipe in a larger bowl for two servings, but add 20 to 30 seconds to the cook time.
- Swap in almond butter or sunflower seed butter if you need a peanut-free version.
Pin it This little mug cake has saved more late nights than I can count. Keep the ingredients on hand and you'll never be more than three minutes from something sweet.
Recipe FAQ
- → Can I use dairy-free milk in this cake?
Yes, almond or oat milk can replace dairy milk without affecting texture or flavor significantly.
- → How do I know when the cake is done microwaving?
The cake is set in the center and has risen. Avoid overcooking to maintain fluffiness.
- → What optional toppings enhance this peanut butter treat?
Chocolate chips, honey drizzle, or a scoop of ice cream complement the flavor beautifully.
- → Can I substitute the all-purpose flour?
For gluten-free needs, use a 1:1 gluten-free flour blend to maintain texture.
- → Is natural peanut butter suitable for this cake?
Yes, natural peanut butter offers a more robust, less sweet flavor enhancing the cake.