Kirbie's Cravings

Flourless Peanut Butter Mug Cake

This single serving microwave flourless peanut butter cake comes out light and fluffy. You won’t miss the flour at all!
photo of flourless peanut butter mug cake

I had the biggest craving for a peanut butter flavored dessert today, so I whipped this up. The recipe is just 4 simple ingredients that you likely have in your kitchen and the cake stays moist for hours so you can enjoy it right away or later on too.
overhead photo of flourless peanut butter mug cake
Do you have a recurring nightmare that you’re still in school and suddenly it’s finals and you’re completely unprepared? Even though I’ve been out of school for a decade, I still periodically have that nightmare. I wonder when, or if ever, it will go away.

I recently have been having a similar series of panic moments over my upcoming book. It’s been a few months now since I turned in the final draft, and every once in a while, I’ll find myself freaking out because I think I messed up one of the recipes even though I tested and retested all the recipes over and over again before turning in the book. That’s what happened when I made this mug cake. I looked up the recipe and noticed that the original recipe I posted two years ago and the one in the book are different.

photo of a spoon dipping into a flourless peanut butter mug cake

So I started panicking, but luckily, it was all for nothing. The recipe does work as written (just like all the other ones I recently freaked out over). It is one of the ones I tinkered and improved upon for the upcoming book.

I really enjoy how easy this recipe is. It expands quite a bit in the microwave before deflating a little after it has cooled. It has a sweet, pleasant peanut butter flavor. It also continues to stay moist for hours and the peanut butter flavor actually becomes more prominent if you let it sit for a few hours, though it tastes great straight from the microwave too.

flourless peanut butter mug cake in a blue mug

You can check out my whole collection of mug cake recipes here.

As mentioned above, this recipe is featured in my new cookbook of nearly 100  mug cakes!


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Update! This recipe is now updated with video.

Flourless Peanut Butter Mug Cake

Servings: 1
Prep Time: 4 minutes
Cook Time: 1 minute
Total Time: 5 minutes
Course: Dessert
Cuisine: American
A single serving flourless peanut butter mug cake that cooks in the microwave!
5 from 2 votes


  • 2 tbsp peanut butter creamy
  • 1/8 tsp baking powder
  • 1 tbsp white granulated sugar
  • 1 large egg


  • Whisk all ingredients into an oversized, microwave-safe mug until batter is smooth. Microwave for about 1 minute. Let cake cool a few minutes before eating.



Serving: 1mug cake, Calories: 312kcal, Carbohydrates: 20.3g, Protein: 13.4g, Fat: 21.2g, Saturated Fat: 4.9g, Sodium: 208mg, Fiber: 1.6g, Sugar: 16g, NET CARBS: 19g

The nutrition information provided are only estimates based on an online nutritional calculator. I am not a certified nutritionist. Please consult a professional nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.

Did you make this recipe?I'd love to see it! Mention @KirbieCravings and tag #kirbiecravings!

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98 comments on “Flourless Peanut Butter Mug Cake”

  1. I just tried this mine wasn’t as fluffy as in the picture but yummy 😕

    • you might have needed to cook it longer. if it’s not quite done enough, it will sink back down and be dense. every microwave is different. try maybe adding 15-20 seconds next time. another thing could be your baking powder. make sure it’s fresh!

  2. Luv luv luuuuuuv it a lot . Easy and delicious 😀

  3. just made this for the first time and it is amazing 

  4. Has anyone tried this with an egg substitute? Like Flax seed?

  5. Just made this because I wanted a little something sweet after lunch.  It was delicious and it had the perfect texture. Thanks!

  6. It works at first try. Spongy and tasty! Used chunky peanut butter, and added 1 tsp of cocoa powder and a dash of vanilla extract as recommended by some commentors. Thanks for sharing it 🙂

  7. Can you do anything other than white sugar?  I don’t do white sugar or corn syrup.  Try to do no sugar other than maybe something like fruit.  I saw you mentioned dark chocolate.  Did you sweeten it with that?

  8. I just tried this recipe today.  It is the first time I tried a mug cake recipe.  It was absolutely delicious.  I subbed out the sugar and just used 1 packet of sweetner and I cooked mine in a bowl so I could add a scoop of double chocolate icecream.  O. M. G. !!!  While I wouldn’t say it was cake (more like a really stiff custard), it will be one of my go to sweet tooth craving late night quick snack without killing my blood sugar recipes.  Thank you!  Its hard to adjust to low carb diet since I found out I’m diabetic.  This could literally save my life!

  9. I made this using Natural Peanut Butter.  I thought the Natural PB would be too dense, but it worked out okay.  Since Natural PB has no sugar in it, I think next time I will add a little more sugar.  Also, Cinnamon and PB is WONDERFUL together!!!  

    Two Tips for your readers:  if you have a kitchen scale that measures in grams, simply weigh your PB.  My package said that 2T is = 32 grams, so I put my bowl on the scale, zeroed out the scale, and scooped PB until the scale read 48 grams.  If you have to use measuring spoons, spray the spoons with Pam (or similar non-stick spray) first, then measure the PB.  It should fall right out of the spoon.  

  10. Would Almond butter work in this recipe?

  11. I just made this, I substituted 2tbls of Xytrol for the sugar (I like sweet) It worked great and wasn’t as sweet as I expected. But much more like cake then I expected, even hubby like it 🙂 Thank you for the great recipe. 

  12. Best mug cake I’ve ever tried! Perfect for my low carb diet! Thank you!

  13. Made this for the first time last night!  Boy was I surprised. Today I made one using Nutella!  Wonderful!!  Tasted like a brownie!  Think I’ll chop up some walnuts in my next cake!

  14. this was my first mug cake and it was yummy cant wait to try different combinations 

  15. Love it????

  16. Delicious! I put peanut butter on top at the end so it would melt and I also put Hershey’s chocolate syrup so I could have a chocolate-peanut butter combo. 

  17. I LOVE it….I used splendor instead of sugar and it came out fine. Very yummy. Thanks for posting..I love mug cakes. Where can I get your cookbook?

  18. Really want to try this but can you use caster sugar instead of granulated sugar?

  19. I made this twice. The first time, I used Truvia and it was a complete disaster. The second time, I followed the directions EXACTLY and it was a perfect moist peanut butter cake. The taste and texture were both perfect. 

  20. Does anyone know how many carbs are in this cake?

    • I do not have that information but caloriecount and myfitnesspal are both great resources for calculating nutritional value for recipes

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