Keto peanut butter mug cake is made with no flour – just peanut butter, egg, baking soda, and a sweetener. It makes a great keto breakfast!
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.
The ingredients needed to make peanut butter mug cake
You’ll only need four simple ingredients to make this tasty treat. 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 baking powder (though I haven’t tested it in this recipe), remember that 1/4 teaspoon of baking soda is equivalent to 1 teaspoon of baking powder.
How to make peanut butter mug cake
It’s so easy! Scroll down to the recipe card for the detailed instructions. Here are the basic steps:
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.
Mix in the sweetener and the baking soda.
Microwave for 30 seconds, then if needed microwave for 10 more seconds. Don’t overcook it!
If you wish, top it with keto whipped cream.
Why I use stevia
I knew that I wanted this cake to be keto and low carb. I also knew that I wanted to use stevia glycerite as a sweetener. One of us can’t really handle sugar alcohols, so Swerve is out of the question.
I believe that stevia is safe. And although many people object to its taste, the glycerite formulation greatly minimizes the bitter aftertaste.
This cake contains no flour
It was important to me to make a peanut butter mug cake that contains no flour. This is actually easy, since nut butters and eggs combine into wonderful baked goods. As in the case of these delicious (but not keto) paleo chocolate muffins.
Results will vary depending on the exact ingredients you use
Based on my attempts, I have a few pointers for you before you try this recipe. The gist of it is that because it relies on peanut butter and on microwave baking, the results of this recipe will greatly vary, depending on what peanut butter you use and on your own microwave.
So as much as I’d like for this peanut butter mug cake recipe to be completely foolproof, I don’t think this is going to happen.
You see, when I tried to make it for the first time, I tried a recipe that I found after a simple Google search.
The cake in the picture looked amazing – so puffy and fluffy! And the recipe had just three ingredients – peanut butter, egg, and sugar. I was excited! But my own cake was disastrous – dry and gummy and yucky.
I noticed that the blogger who posted that recipe received a few comments complaining about the texture of the cake. Yet I do not doubt for a second that in her kitchen, for her, the cake turned out amazing.
It’s just that there are so many variables when making this cake.
The peanut butter you use makes a difference
The most important is the peanut butter you use. I used Trader Joe’s creamy salted peanut butter. This is a natural peanut butter that contains just peanuts and salt.
After you stir it well, it tends to be quite runny, until you get to the bottom where there’s some drier residue (despite your best efforts at mixing it well).
So the top portion of this jar will yield a moister peanut butter mug cake than the bottom portion. And it will also be easier to mix with the egg. And if you use no-stir peanut butter, your results might be completely different.
The best advice I can give you is to go by how the mixture looks and feels in your kitchen, with your peanut butter. Even with the Trader Joe’s peanut butter, I have found that the mixture feels too sticky to me.
So I add a tablespoon of water and then it’s perfect. With another brand of peanut butter, you might need to add a little more water, or none.
I show you in the video below how the mixture looks right before I microwave it. You can see that it’s very smooth, shiny, and not too thick. I hope this helps.
The size of the egg makes a difference too
Another variable in this peanut butter mug cake recipe is the egg you use. I typically use a large egg, but I tend to pick one on the smaller side. Have you noticed how in a carton of large free-range eggs there are pretty big variations in size?
Some eggs are much smaller than others. So I usually pick an egg that I would still classify as large, but is one of the smaller eggs in the carton.
You will probably need to add some water
As I said, I add at least one tablespoon of water to the mixture, because otherwise, the mixture feels too thick and sticky. I usually start mixing the peanut butter and egg. I quickly get frustrated at how sticky and impossible the whole thing is.
Then I add water, which makes the task significantly easier and creates a much smoother batter. I would say, however, that if your batter feels nice and smooth and not very sticky and thick, it’s possible that you don’t need to add water.
Should you add salt to peanut butter mug cake?
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.
How long to microwave the cake?
This is another big variable. How powerful is your microwave? As a general rule, it’s always best to err on the side of microwaving less. You can always add microwave time to a cake that’s too moist, but once a cake is super dry, then it’s ruined.
I always start with 30 seconds, then 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 this cake.
Mix the batter well!
The only challenging part about making this recipe is that you need to mix the peanut butter and egg really well until the mixture is completely smooth and uniform.
This is not an easy task. If you feel that it’s nearly impossible, or if after mixing your batter seems very thick and sticky, I suggest adding a tablespoon of water to the mixture. This makes mixing much easier.
What dish to use?
This seems to be more 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.
Isn’t that a lot of calories for a single-serve cake?
Yes and no. At 470 calories, this is not a low-calorie cake, by any means. I agree that it’s a bit too much for dessert (unless you share it).
But I actually have this cake as my breakfast. After all, it’s basically just peanut butter and an egg – and for me, a 500-calorie breakfast is perfect. It is also very satiating and keeps me full for many hours.
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Peanut Butter Mug Cake
INGREDIENTS
- 1/4 cup natural creamy peanut butter (only ground peanuts and salt)
- 1 large egg
- 1/2 teaspoon stevia glycerite (equals 2 tablespoons sugar)
- 1/4 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 peanut butter mug 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:
More Recipes to Try:
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, Reader's Digest, and Better Homes and Gardens.