This amazing keto peanut butter mug cake is made with no flour - just peanut butter, egg, baking soda, and a sweetener.
Ready in about five minutes, it makes a great keto breakfast or snack. Add a few chocolate chips or top it with whipped cream and it's the perfect dessert!
I've been working on this cake for a while now. It's a simple cake with only four ingredients, but since nut butters greatly vary in their texture, it wasn't that easy to get the ratios right.
So it took me several tries until I perfected this recipe. But I did eventually reach perfection - a tasty, gooey and moist cake with just the right amount of sweetness. I really like it for breakfast!
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Ingredients
You'll only need four simple ingredients to make this keto peanut butter mug cake. The exact measurements are included in the recipe card below. Here's an overview of what you'll need:
Peanut butter: Use natural creamy peanut butter. I use Trader Joe's, which contains peanuts and salt.
Egg: I use large eggs in most of my recipes, including this one.
Sweetener: I like stevia. You could try using a granulated sweetener instead, but I haven't tried that.
Baking soda: If you'd like to try using gluten-free baking powder (though I haven't tested it in this recipe), remember that ¼ teaspoon of baking soda is equivalent to 1 teaspoon of baking powder.
Instructions
Making this keto peanut butter mug cake is easy! Scroll down to the recipe card for detailed instructions. Here are the basic steps:
You start by mixing the peanut butter with the egg in a medium mug until completely incorporated. You might need to add a bit of water.
The next step is to mix in the sweetener and the baking soda.
Now, microwave the cake for 30 seconds, then if needed microwave for 10 more seconds. Don't overcook it! And if you wish, top it with keto whipped cream.
Expert tips
Based on my attempts, I have a few pointers for you before you try making this cake. The gist of it is that because this recipe relies on peanut butter and on microwave baking, the results will greatly vary, depending on what peanut butter you use and on your own microwave.
- Use a freshly opened jar of natural peanut butter and stir it well. If you opt for a half-used jar, the peanut butter might be too dry.
- Go by how the mixture looks and feels in your kitchen, with your peanut butter. I show you in the video - it should be smooth, shiny, and not too thick. If it's sticky and difficult to mix, add an extra tablespoon of water.
- I don't add salt to the batter, because my peanut butter is already salted. If your peanut butter contains just peanuts and nothing else, not even salt, add a pinch of salt to the batter.
- Microwaves vary. I always start with 30 seconds, check the cake, then usually add 10 more seconds. By then, the edges are puffed and the center is still gooey - and that's exactly how I like it.
- You need to mix the peanut butter and egg really well until the mixture is completely smooth and uniform. If the batter is very thick and sticky, add a tablespoon of water. This makes mixing much easier.
Frequently asked questions
Yes! I was suspicious too when I first started making them. But they do work, and they produce results that are very close to a true cake crumb - tender, fluffy, and sweet.
This seems to be fairly flexible. I have made this cake in several dishes. A small and tall 10-oz mug, a wide 15-oz mug, and a 3.5-inch-wide ramekin (as shown in the video and in the photos).
They all worked, and there wasn't much of a difference. Except that with the ramekin, I was worried there for a moment that the batter might overflow! But it didn't. You can always place your mug on a microwave-safe plate to catch possible spills.
Yes. Let it cool completely on a cooling rack, then wrap the mug with plastic wrap and then with a layer of foil. Freeze for up to three months. You can defrost it in the microwave, after removing the layers of foil and cling wrap.
Variations
I love this recipe as is and almost always make it as written. But in case you'd like to vary the basic recipe, here are a few ideas for you:
- Add a few drops of pure vanilla extract to the batter. It goes nicely with the peanut butter flavor.
- Mix a few chocolate chips into the batter before microwaving it.
- If you like cinnamon, try adding a pinch of it to the batter. Not everyone enjoys this flavor combination, though!
Serving suggestions
This cake is wonderful all by itself, and when I don't add anything to it, I feel that it makes the perfect keto breakfast.
When I want to make it for dessert, I usually top it with keto whipped cream or with chocolate whipped cream.
It's also good drizzled with melted dark chocolate.
Storing leftovers
You can store the completely cooled leftovers in the fridge for up to 4 days (provided you didn't top the cake with whipped cream). You can leave the cake in the mug and wrap the mug in two layers of cling wrap.
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Recipe card
Keto Peanut Butter Mug Cake
INGREDIENTS
- ¼ cup natural creamy peanut butter (only ground peanuts and salt)
- 1 large egg
- ½ teaspoon stevia glycerite (equals 2 tablespoons sugar)
- ¼ teaspoon baking soda
INSTRUCTIONS
- In a medium mug or a large ramekin, mix the peanut butter with the egg until completely incorporated. Check especially on the bottom to make sure there is no peanut butter residue.
- If the batter seems very thick, sticky and stubborn, add a tablespoon of water and keep mixing until completely smooth.
- Mix in the stevia, then the baking soda. Mix well.
- Microwave the cake for 30 seconds. Check it - if it looks very wet, add 10 more seconds. I usually stop at this point - the edges are puffed and done but the center is still gooey. That's how I like it!
- Enjoy the cake as is, or top it with a dollop of whipped cream for a truly rich experience.
WATCH THE VIDEO:
NOTES
- Use a freshly opened jar of natural peanut butter and stit it well. If you use a half-used jar, the peanut butter might be too dry.
- Go by how the mixture looks and feels in your kitchen, with your peanut butter. I show you in the video - it should be smooth, shiny, and not too thick. If it's sticky and difficult to mix, add an extra tablespoon of water.
- I don't add salt to the batter, because my peanut butter is already salted. If your peanut butter contains just peanuts and nothing else, not even salt, add a pinch of salt to the batter.
- Microwaves vary. I always start with 30 seconds, check the cake, then usually add 10 more seconds. By then, the edges are puffed and the center is still gooey - and that's exactly how I like it.
- You need to mix the peanut butter and egg really well until the mixture is completely smooth and uniform. If the batter is very thick and sticky, add a tablespoon of water. This makes mixing much easier.
- I have made this cake in several dishes. A small and tall 10-oz mug, a wide 15-oz mug, and a 3.5-inch-wide ramekin (as shown in the video and in the photos). They all worked, and there wasn't much of a difference. Except that with the ramekin, I was worried there for a moment that the batter might overflow! But it didn't. You can always place your mug on a microwave-safe plate to catch possible spills.
ADD YOUR OWN NOTES
NUTRITION PER SERVING
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Vered DeLeeuw, LL.M., CNC, has been following a low-carb real-food diet and blogging about it since 2011. She's a Certified Nutrition Coach (NASM-CNC), has taken courses at the Harvard School of Public Health, and has earned a Nutrition and Healthy Living Certificate from Cornell University. Her work has appeared in several major media outlets, including Healthline, HuffPost, Today, Women's Health, Shape, and Country Living. 
