Giant Peanut Butter Jar Cake

The first thing I do when I hop off the plane at LAX is go straight to Costco! I LOVE that place (giant amounts of food for a wholesale price? I’m in!). My love of peanut butter, this huge empty plastic container, and my imagination lead me to this amazing over the top cake. This is my GIANT Peanut Butter Jar Cake! This cake might seem intimidating, but it’s not too hard, I promise! If you LOVE peanut butter, check out my Giant Peanut Butter Cup and my Peanut Butter Shooters!

For this recipe, you’ll need four batches of my vanilla cake. You can find that recipe here. You’ll also need my perfectly pipeable buttercream frosting. You can find that recipe here. I know the great debate is chunky vs smooth peanut butter, but in this case I would only recommend using smooth peanut butter for this recipe (trust me, you won’t regret it)!


  1. Add ¾ white chocolate to ¼ milk chocolate. Microwave in 30 second intervals and stir in between until it’s melted.
  2. Add yellow food colouring and stir well.
    pb mixture
  3. Use a craft/exacto knife to cut your oversized container in half horizontally.
    pb cake mold
  4. Pour the chocolate batter into each half. Coat the inside evenly with a layer of chocolate, and transfer to the fridge to set.
  5. Once set, add another layer of chocolate and let it set in the fridge.
    jar coating
  6. Add peanut butter to a double batch of buttercream frosting. Mix well.
    peanut butter buttercream
  7. Use an 8 inch cake tin as a guide to cut around the vanilla cakes. Cut two and a half circles from the cake sheet.
    pb cake carve
  8. Use a cake leveler to level off your 6 cake pieces so that they’re the same height. Trim away any brown layers using a serrated edge knife.
  9. Brush simple syrup (part water part syrup) on top of the cakes.
  10. Remove your containers from the fridge. Make 2 slits in each piece of plastic, and peel it away from the chocolate mold.
    pb mold remove
  11. Heat up a skillet. Place the hot skillet on the top edges of each half of the chocolate mold.
    skillet mold
  12. Spread your peanut butter frosting to the inside of your mold.
  13. Place a layer of cake. Then, add frosting over that cake layer. Top with a layer of peanut butter cups! Finally, add another layer of frosting to fill in any gaps.
    cake frosting pb cups frosting
  14. Repeat this with the rest of your cake pieces. On the top layer, stack the peanut butter cups upside down.
  15. Transfer to the fridge for 30 minutes.
  16. Place thick milkshake straws into the bottom half of your cake. Cut them so that they are almost level with the cake. Place a cake board over the straws, and use frosting to secure it in place.
    straws pb cake
  17. Use your hot skillet again on both of the edges to secure them into place.
  18. Flip your top half onto your bottom and line them up. Place chocolate in a snap seal bag, and fill any gaps with the chocolate. Run your fingers around the edges where they met.
    pb jar cake join
  19. Roll out your yellow fondant, cut around the actual lid from the jar for reference.
  20. Roll out a long piece of yellow fondant, and roll the lid against it to make grooves along the piece.
    pb jar lid
  21. Brush water onto the yellow fondant pieces and secure them onto the top of the cake.
  22. Wrap your template around your cake, and secure it with a piece of tape.
    pb label

What You’ll Need:

-Watch the full video on YouTube
-Buy the My Cupcake Addiction Cookbook
-Subscribe to my YouTube channel for 2 new videos each week!
-Follow me on Facebook for short snappy sweet ideas daily!
-Share your sweets with me on Instagram Use the #mycupcakeaddiction so I can see them & I’ll re-share some of my favorites!
-Sign up to our #SweetSquad for early access, exclusive offers and fun party planning tips

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