Behold the Peanut Butter Fudge Brittle Cake!
Peanut butter cake layers with a new recipe for peanut butter fudge filling
And of course no cake is ever complete without buttercream! Peanut Butter buttercream to be exact!
It’s quite the grand project but the results are well worth the effort!
The moistness that comes through to this cake recipe when using flax meal as the egg replacer is just unmatched!
Oh yeah, and if you’re just here for the Peanut Brittle
I’ve got that too!
Notes for Success:
IN THE VIDEO WHERE I SAID HARD CRACK STAGE FOR PEANUT BRITTLE IS 270°F – THE CORRECT TEMPERATURE TO COOK IT IS 300°F
A total of four recipes are needed to make this entire cake, but they can all be made ahead of time
The cake can be baked the day before and wrapped and refrigerated until needed and ganache can be made up to a week ahead
Same goes for the peanut butter fudge filling!
If you are like me you always have buttercream stashed away in the refrigerator
But if not, that can also be made up to a week ahead!
When you are ready to build just follow along ion the video below!
CLICK HERE FOR THE FULL YOUTUBE VIDEO TUTORIAL FOR STEP BY STEP INSTRUCTIONS TO COMPLETE THIS CAKE
Peanut Butter Fudge Brittle Cake

Ingredients
- 1 Recipe Aquafaba Swiss Buttercream
- 1 cup Peanut Butter
- OR ½ cup peanut butter powder
- ½ Recipe Fudge Icing
For the Cake:
- Vegan Butter 1 cup + 2 tablespoons (255g)
- Granulated Sugar 2¼ cup (450g)
- Creamy Peanut Butter 1 cup (240g)
- Flax Meal 5 Tablespoon (40g)
- Warm Water ¾ cup (180ml)
- Vanilla Extract 3 teaspoon (15ml)
- Plant Milk ¾ cup (180ml)
- Vinegar 1 Tablespoon (15ml)
- All Purpose Flour 2½ cups (312g)
- Baking Powder 1¼ teaspoons
For the Peanut Butter Fudge:
- Peanut Butter 1 cup (240g)
- Corn Syrup or Agave 1½ cup
- Coconut Oil or Vegan Butter ¼ cup (56g)
- Vanilla Extract 2 teaspoon (10ml)
- Creamy Peanut Butter 1 cup
- Agave Syrup ½ cup
- Coconut Oil ½ cup
- Vanilla Extract 1 teaspoon (5ml)
For the Peanut Brittle:
- Sugar 1 cup (200g)
- Corn Syrup ½ cup (120ml)
- Water ¼ cup (60ml)
- Vegan Butter 2 Tablespoons (28g)
- Baking Soda 1 teaspoon
- Unsalted Raw Peanuts 1 cup (150g)
- ¼ Recipe Ganache
Instructions
- Prepare the buttercream as listed on the blog post for that recipe and add the peanut butter at the last stage of mixing.
- Prepare the fudge icing as well and reserve until needed
- Prepare the ganache about an hour before you are ready to assemble the entire cake, or make ahead and rewarm when needed
- For the Cake:
- Preheat the oven to 350°F and grease and parchment paper 4-7" cake pans or 2-8" cake pans
- Sift the flour with the baking powder
- Combine the flax meal with the warm water and set aside to thicken about 5 minutes.
- Add the vinegar to the plant milk
- Cream the semi soft room temperature vegan butter with the sugar on medium to high speed until fluffy about 3-5 minutes.
- Add the peanut butter and mix well
- Add the vanilla extract
- Add the flax paste and then whip on high speed to emulsify for 10 seconds
- Next add about 1/3 of the flour mixture and mix just until it is incorporated
- Then add about half of the plant milk mixture, mixing to combine not even until all the flour has disappeared
- Add another 1/3 of the flour and then the rest of the milk mixture
- Ending with the last addition of flour being careful not to over mix after each addition, The entire process should not take more than 1 minute
- Divide evenly between the prepared pans and bake for approximately 28-30 minutes or when they are springy to the tough when you gently press the centers
- For the Peanut Butter Fudge:
- Combine the peanut butter and agave or corn syrup in a heavy bottom sauce pot and bring to a boil stirring constantly.
- Boil for about 1 minute then add the coconut oil and vanilla extract and transfer to a bowl to cool
- For the Peanut Brittle:
- Combine the sugar, corn syrup and water in a heavy sauce pot and bring to a boil.
- Once it boils, Insert a candy thermometer and continue to boil without stirring until it is 300-309°F (*See notes above about my speaking error in the video) it should just start to turn golden brown, then add the vegan butter, baking soda, vanilla extract and peanuts.
- Stir well to combine
- Spread mixture on a lightly oiled sheet pan and let cool then crack it up to jagged pieces
- Assemble cake as shown in the video
Notes
This cake can be stored at room temperature for up to 3 days in a cool spot or for longer storage refrigerate in an airtight container for up to 1 week.
Best served room temperature
This has to go down as one of your most amazing creations. Looks delicious – and dangerous. How can you eat just one slice? That’s why I’ll make the cupcakes.
I just bought flax seeds to try your recipes. Is it still okay to put the flax seed in the coffee grinder to make my own flax meal?
yes that is the best way to do it if you are not using them quickly, since they have a high Omega 3 fat count, they can go rancid quick, so store them in the freezer and grind them as you need.
Hi Gretchen. I have been following you since the beginning. I love your recipes. I am not vegan. I would like to know if I make these recipes and I use butter eggs buttermilk etc as substitutes will the products come out ok. Thanks for everything.
thanks! Yes you can use cow dairy for everything I use plant based, and the eggs.. Hmm I say do 2 (Just be aware that as I stated in the video this recipe really does benefit from the flax, and that is why I recommend to use it instead of eggs – of course aside from the vegan aspect, it just really is better with flax)
Great PB cake recipe, my layers came out quite flat though and I’m not sure what i did wrong! The PB fudge is amazing! Thanks Gretchen!
Hi, I’m a little confused on the peanut brittle. The recipe states 60ml water and 120ml corn syrup, but the written instructions and video don’t mention the corn syrup.
Oh wow how embarrassing! thanks for catching that! I have updated the post!
Ingredients are correct: Sugar 1 cup (200g)
Corn Syrup ½ cup (120ml)
Water ¼ cup (60ml)
Vegan Butter 2 Tablespoons (28g)
Baking Soda 1 teaspoon
Unsalted Raw Peanuts 1 cup (150g)
Method:
Combine the sugar, corn syrup and water in a heavy sauce pot and bring to a boil.
Once it boils, Insert a candy thermometer and continue to boil without stirring until it is 309°F (*See note above) it should just start to turn golden brown, then add the vegan butter, baking soda, vanilla extract and peanuts.
Spread mixture on a lightly oiled sheet pan and let cool
Hi Gretchen, it looks like there are two sets of peanut butter fudge ingredients on here? I will be using corn syrup and butter, which recipe should I use? Thank you!
I took this cake out of the oven an hour ago, couldn’t help cutting a small taste off the top before it goes into the freezer to stack and fill another day…but I had to leave a review for this because it was so good that it is easily the best dessert I’ve eaten all YEAR. It is best described as the best peanut butter cookie you have ever had in your life in cake form. So if anyone reading this is on the fence, go, run and get your peanut butter!🙌
wow! Thanks for the review!