If you also think mint and chocolate is a perfect match, you’ll love this Mint Chocolate Chip Sheet Cake with a thick, fluffy chocolate cake and creamy mint chip buttercream frosting!

It’s time for the March edition of Sheet Cake of the Month, and we’re going green and minty with a Mint Chocolate Chip Sheet Cake! (Yes, mint and green are overplayed in March for St. Patrick’s Day, but I knew I knew I wanted to make this cake sometime during this series, so why not lean into the green everything trend?)

Mint chocolate chip is one of those classic flavor combinations that never goes out of style. Whether it’s a scoop of ice cream on a hot summer day or peppermint desserts during the holidays, it’s always a winner. And that’s exactly what this Mint Chocolate Chip Sheet Cake delivers: an ultra-soft chocolate cake infused with just the right amount of mint, topped with a creamy mint buttercream packed with chopped mint candies. It’s easy to make, serves a crowd, and perfect for any occasion!

I love this cake for parties, birthdays, or even just a fun weekend baking project. Since it’s made in a 9×13-inch pan, there’s no need to worry about stacking layers or complicated decorating. Just bake, frost, slice, and serve! And if you’re a fan of mint chocolate desserts, this cake is right up there with mint brownies, grasshopper pie, and peppermint bark when it comes to satisfying that chocolate-mint craving.

Ingredients and Substitutions

• All-Purpose Flour: For a gluten-free version of this cake, use a 1:1 gluten-free flour blend containing xanthan gum.
• Granulated Sugar
• Cocoa Powder: Use natural unsweetened cocoa powder for this cake, not Dutch processed cocoa powder.
• Baking Soda
• Baking Powder
• Salt
• Eggs: Let the eggs sit out at room temperature for 20-30 minutes before making the cake batter.
• Buttermilk: This cake is truly best with real buttermilk. An easy 1:1 substitution is kefir. In an emergency, using 1 1/2 cups of whole milk with 2 tablespoons of lemon juice will provide an acidic base, but the texture of the cake is not as fluffy.
• Coffee: Hot coffee makes the chocolate taste extra chocolatey and helps the cocoa powder bloom. Hot water can be used as a substitute.
• Oil: Use a neutral-flavored oil, like vegetable, grapeseed, or avocado oil.
• Vanilla Extract
• Mint Extract: Use pure mint extract, not peppermint or spearmint extract, for the classic mint chocolate chip flavor.
• Butter: Unsalted butter at cool room temperature (~65°F)
• Confectioners’ Sugar
• Heavy Cream: Heavy cream creates the best frosting texture, but half-and-half of whole milk can work in a pinch.
• Green Food Coloring: While optional, I always think mint chocolate chip desserts should be green!
• Chopped Chocolate Mints: Andes are classic, but Junior Mints, peppermint bark, mint chocolate chips, or large chocolate mints all work here – or use a chopped chocolate bar, shaved into small bits

How to Make Mint Chocolate Sheet Cake

1. Prep Dry and Wet Ingredients: Whisk together the flour, sugar, cococa powder, baking powder, baking soda, an salt. In a separate bowl, whisk the eggs, buttermilk, coffee, oil, vanilla extract, and mint extract.

2. Make the Cake Batter: Slowly add the wet ingredients to the dry, stirring until just combined.

3. Bake the Cake: Pour the batter into a 9×13-inch pan and bake until a tester comes out clean. Cool the cake completely.

4. Make the Frosting: Beat the butter until smooth, then add 1 cup of confectioners’ sugar and a tablespoon of heavy cream, mixing on high speed for a minute. Repeat with the rest of the sugar and cream. Add the salt, mint extract, and green food coloring and mix on high for an additional minute. Fold in the chopped chocolate mints.

5. Frost the Cake: Spread the buttercream evenly over the cooled cake and decorate with additional chopped mints, chocolate shavings, or chocolate sprinkles, as desired.

Oil or Butter in Cakes?

You know I always like to include a little bit of the chemistry behind baking in each post (I am a scientist, after all!) and today I thought we’d tackle a common question: when to use butter versus oil in a cake. Yes, butter provides superior flavor: we all know the rich, creamy, delicious flavor of a buttery cake. But! For the best texture, oil is superior. In a chocolate cake, we’re getting most of the flavor from the cocoa powder, so we want to choose fat for the texture!

Kitchen Chemistry

Butter is roughly 20% fat and 20% water, while oil is 100% fat. The extra fat content in oil coats flour particles more efficiently, reducing gluten development and keeping the cake soft. Furthermore, oil remains liquid at room temperature, ensuring a more consistently moist cake compared with butter-based cakes, which can feel firmer, especially when chilled.

Chocolate cakes, in particular, benefit from using oil because cocoa powder naturally absorbs a lot of moisture. And with sheet cakes, which are usually served straight from the pan (no stacking or coating all the sides with frosting to lock in moisture), using oil helps it stay soft for days. Whether you’re making this cake ahead of time or planning on enjoying leftovers, the oil-based structure ensures every bite stays as just delicious as the first!

Tips and Tricks for the Best Mint Chocolate Chip Sheet Cake

1. Don’t Overmix!: Mix just until the ingredients are combined to avoid a dense cake.
2. Use the Right Mint Extract: Use mint extract, not peppermint or spearmint extract, for a classic mint chocolate chip flavor. Regular mint extract uses a combination of spearmint and peppermint, which pairs better with chocolate.
3. Cool Completely Before Frosting: Frosting a warm cake will cause the buttercream to melt.
4. Adjust the Mint Flavor: Mint extract can be strong, and different brands vary in intensity. Start with a small amount in the frosting, then add more to taste.
5. Chop the Mint Candies: Whether you’re using Andes mints, junior mints, or another brand, chop them into small bits. Large chunks can make frosting the ake difficult.
6. Chill Before Cutting: If you want nice, sharp slices, pop the frosted cake into the refrigerator for 20-30 minutes before slicing. This helps firm up the buttercream for neater cuts.
7. Storage: The cake stays fresh at room temperature for up to 4 days, in the refrigerator for up to a week, or can be frozen for up to 3 months.
8. Recommended Tools: Cake Pan | Stand Mixer | High Quality Cocoa Powder | Mint Extract | Offset Spatula

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