This amazing keto peanut butter mug cake is made with no flour. 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. It took me several tries, but I eventually reached perfection - a tasty, gooey, and moist cake with just the right level of sweetness.
Ingredients
You'll only need four simple ingredients to make this 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, but you can use a granulated sweetener instead.
- Baking soda: You can replace it with a teaspoon of baking powder (gluten-free if needed).
Variations
- 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, add a pinch to the batter. Not everyone enjoys this flavor combination, though!
Instructions
Scroll down to the recipe card for detailed instructions. Here are the basic steps for making this cake:
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 baking soda.
Microwave the cake for 30 seconds. If needed, microwave it for 10 more seconds. Don't overcook it! If you wish, top it with keto whipped cream before serving.
Expert Tips
Based on my attempts, I have a few pointers for you before you make this cake. The gist is that because this recipe relies on peanut butter and microwave baking, the results will greatly vary, depending on what peanut butter you use and on your 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.
- 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 should mix the peanut butter and egg thoroughly 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. The photo below shows you how the batter should look - smooth, shiny, and not too sticky.
Recipe FAQs
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 real cake crumb - tender, fluffy, and sweet. The photo below shows you the beautiful, tender crumb of this cake. 
You have some flexibility here. I have made this cake in several dishes. A small and tall 10-ounce mug, a wide 15-ounce 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. You can use natural almond butter in this recipe. If you do, I recommend adding ¼ teaspoon of almond extract to the batter.
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 chocolate whipped cream. It's also good drizzled with melted dark chocolate.
Storing Leftovers
You can store the 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.
You can also freeze this cake. Let it cool completely on a cooling rack, then wrap the mug with plastic wrap, followed by a layer of foil. Freeze the cake for up to three months. You can defrost it in the microwave after removing the layers of foil and cling wrap.
More Keto Mug Cakes
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Recipe Card
Keto Peanut Butter Mug Cake
Video
Ingredients
- ¼ cup natural creamy peanut butter - only ground peanuts and salt
- 1 large egg
- ½ teaspoon stevia glycerite - equals 2 tablespoons of sugar
- ¼ teaspoon baking soda
Instructions
- In a medium mug or a large ramekin, mix the peanut butter and 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.
Notes
- Use a freshly opened jar of natural peanut butter and stir 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. 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.
- I have made this cake in several dishes. A small and tall 10-ounce mug, a wide 15-ounce 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.
- Occasionally, baking soda can cause a reaction in baked goods that results in an ammonia smell. If you're concerned about it happening, use 1 teaspoon of baking powder (gluten-free if needed) instead of baking soda. Make sure the baking powder is fresh and not expired.
- You can store the 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.
- You can also freeze this cake. Let it cool completely on a cooling rack, then wrap the mug with plastic wrap, followed by a layer of foil. Freeze the cake for up to three months. You can defrost it in the microwave after removing the layers of foil and cling wrap.
Nutrition per Serving
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Most recipes are low-carb and gluten-free, but some are not. Recommended and linked products are not guaranteed to be gluten-free. Nutrition info is approximate. Please verify it independently. The carb count excludes non-nutritive sweeteners. Please read these Terms of Use before using any of my recipes.
maria says
Surprised but really good. I used cashew, almond, peanut butter. Thank you!!
Vered DeLeeuw says
You're very welcome, Maria!
Flkitten says
I just tried this and it turned out fantastic! it's so moist and tasty! I used 3 pumps of skinny girl pumpkin praline syrup instead of the liquid stevia. I'm definitely going to make this often!
Vered DeLeeuw says
I'm so glad you enjoyed this mug cake! Thank you for leaving a comment.
MCC says
I use vanilla extract, allulose sweetener and a little swerve brown sugar, a tablespoon of heavy whipping cream for moisture, and mix in a few Reese’s peanut butter morsels.
Vered DeLeeuw says
Sounds great! Thanks for sharing your version.