Kirbie's Cravings

Chocolate Peanut Butter Lava Mug Cake

This flourless molten chocolate mug cake has a creamy peanut butter lava center. It’s an easy dessert that cooks in the microwave in less than 1 minute! The cake is naturally gluten-free and can be adapted for a low carb diet.

overhead photo of a molten lava cake

This mug cake is a bit different from most of the chocolate peanut butter lava mug cakes I’ve come across. Most of the ones I’ve seen have a chocolate cake base with melted peanut butter in the center. For my mug cake, the chocolate cake is not your classic fluffy chocolate cake. Instead, I use a molten chocolate cake recipe so it really tastes like molten chocolate cake.

Because the cake is cooked in the microwave, the center doesn’t stay molten like when the cake cooks in the oven. But it still tastes pretty darn delicious. And to create that molten lava center, I decided to add some creamy peanut butter.
close-up photo of a chocolate peanut butter lava cake in a mug

How to Make a Chocolate Peanut Butter Lava Cake

  • Melted butter, heavy cream, and an egg are whisked together. Then, cocoa powder and sugar are mixed into the batter.
  • Spoon a tablespoon of peanut butter into the center of the batter. You don’t need to push it down because it will naturally sink down as the cake cooks.
  • Let the cake cook for about 45 seconds to 1 minute. You want the cake to fluff up and pull away from the edges of the mug. It’s okay if the edges still look gooey and not completely set since this is a lava cake.

Serving the Cake

  • You can serve this like a classic lava cake by turning your mug upside down and letting the cake slide onto a plate. Because the edges of the cake are still liquid, the liquid will pour on top of the cake, creating a delicious liquid chocolate glaze.
  • You can also eat the cake as is, straight out of the mug.

Tips for Making a Lava Mug Cake

  • If you plan on plating this, I recommend using a wide oversized mug, so that the cake will resemble the shape and size of a typical lava cake.
  • A few seconds in the microwave can make a huge difference. I recommend starting at 40 seconds and then increasing at 5 second intervals. If you cook the cake too long, it will be completely cooked, including the peanut butter center.
  • I don’t recommend using more than 1 tbsp of peanut butter. If there is too much peanut butter, it will be too heavy and just sink to the bottom of the mug.

Can this Mug Cake be Baked in the Oven?

Yes. Grease an 8 oz ramekin. Pour batter in and bake in oven at 350F for about 10-15 minutes or until edges are set and center of the cake is still slightly liquid and not yet set.

close-up photo of a lava cake on a plate
Looking for more mug cakes to try? I have a huge collection of mug cake recipes including a Peanut Butter Chocolate Chip Mug Cake and a Flourless Peanut Butter Mug Cake.

Chocolate Peanut Butter Lava Mug Cake

Servings: 1
Prep Time: 4 minutes
Cook Time: 1 minute
Total Time: 5 minutes
Course: Dessert
Cuisine: American
A molten chocolate cake with a creamy peanut butter center. This cake is prepped in a mug and cooks in the microwave in less than 1 minute.
4.67 from 3 votes


  • 1 tbsp unsalted butter
  • 1 tbsp heavy cream
  • 1 large egg
  • 2 tbsp unsweetened cocoa powder
  • 2 tbsp granulated white sugar
  • 1 tbsp creamy peanut butter


  • Add butter to a large microwave-safe mug. Melt in microwave. It is important to add the butter first because it will also help grease the bottom of the mug.
  • Add in heavy cream and whisk. Adding the heavy cream in next will help cool down the butter so it is not too hot when you add in the egg.
  • Add egg and whisk until batter is smooth. Make sure there are no egg white streaks at this stage. If you wait until you add the cocoa, you will no longer be able to see if there are any unmixed egg streaks.
  • Add cocoa powder and sugar. Whisk until batter is smooth.
  • Add 1 tbsp of peanut butter to the center of the batter. When dropping the peanut butter in, I recommend trying to spread the peanut butter out a little so that it is not dropped all on the same spot. So for example, add about 1/2 a tbsp to the very center of the batter. Then add 1/4 tbsp slightly to the right of that first dollop and add remaining 1/4 tbsp slightly to the left of that dollop. This ensures peanut butter throughout the middle and not just in one small spot. Do not push the peanut butter down into the batter. Doing so will cause the peanut butter to completely sink to the bottom. The peanut butter will sink in gradually as it cooks.
  • Cook the cake at full power in the microwave for about 45-60 seconds or until center fluffs up and looks set, but edges remain slightly gooey. Because the cake cooks very fast, I recommend cooking for 40 seconds and then checking on the cake. Continue to cook at 5 second intervals. I used a 1100 watt microwave. You may need to adjust your microwave power or time if your microwave is a different wattage.
  • Flip mug upside down to pour cake onto a plate. The remaining gooey batter should pour on top of the cake like a glaze. You can also skip plating and eat the cake directly from the mug.


  • You can replace the sugar with a sugar substitute like erythritol. You will likely need to add more erythritol to equal 2 tbsp of sugar.
  • I used a 1100 watt microwave. If your microwave has a different wattage, you will need to adjust cooking time or power.
  • The cake cooks very fast. I recommend stopping at 40 seconds to check on it and then cooking at 5 second intervals, otherwise the cake could easily overcook. My cake took about 50 seconds total.
  • Unlike a traditional lava cake, this cake will cook first in the center and the edges will be the last to finish cooking. You will want the center to fluff up and be set but the edges to still be gooey.
  • It's okay for the edges of the cake to still be gooey. The remaining molten batter will pour over your cake, giving you some of that molten liquid chocolate. You don't want the cake to cook all the way because then the peanut butter in the center will overcook and no longer be creamy. 
  • I recommend using a creamy, natural peanut butter as it will be easier to spoon into the center of the batter.
  • Some of the peanut butter will likely leak to the bottom of the cake when it cooks. This is normal. As long as you don't push down on the peanut butter before cooking the cake or don't add too much peanut butter, most of the peanut butter will stay in the cake. The part that leaks through will just be a molten peanut butter cover on top of the cake when you flip it onto a plate.
  • I recommend using a large oversized mug where the bottom resembles the shape and size of an 8 oz ramekin so that your cake will look similar to a baked ramekin version.
  • This cake can be cooked in the oven. Cook the cake in a greased 8 oz ramekin at 350F for about 10-15 minutes or until edges are set and middle is not set.
  • Nutrition is calculated using sugar. If you use a sugar substitute, the carb count and calorie count will be less.


Serving: 1cake, Calories: 429kcal, Carbohydrates: 35g, Protein: 14g, Fat: 30g, Saturated Fat: 12g, Sodium: 90mg, Fiber: 5g, Sugar: 25g, NET CARBS: 30

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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Recipe Rating

8 comments on “Chocolate Peanut Butter Lava Mug Cake”

  1. I really liked this especially since it had no flour. It tasted great!

  2. omg just made this, it was amazing !

  3. Love it! ? Made it keto and dairy free by using avocado oil in place of butter, coconut milk in place of milk and monk fruit in place of sugar. I also froze globs of peanut butter to toss in so it doesn’t get overcooked. Delish!

  4. I used avocado oil and coconut cream. I also froze a glob of peanut butter. Microwaved it for 50 sec. Turned out great!!