Thin Mint Brownies

Intensive Cake Unit
by Intensive Cake Unit
1 9x13 pan
50 min

Sometimes I need a dessert that’s simple and goes together quickly! A decorated 9x13 sheet pan of cake or brownies can easily be made from scratch OR doctored-up mixes, and they’re easy to decorate, festive, delicious, and can serve a large crowd!

It’s Girl Scout cookie season, and I got several boxes of cookies recently from my nieces – including two boxes of Thin Mints! I needed a way to get them out of the house before I ate both of them by myself….so onto a pan of brownies they went! HUGE hit when I took them to work; they were gone soo fast! Recipe(s) below!

Recipe details
  • 1  9x13 pan
  • Prep time: 20 Minutes Cook time: 30 Minutes Total time: 50 min
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  • 1 cup unsalted butter (or 2 sticks) melted
  • 1 cup granulated sugar
  • 1 cup brown sugar
  • 4 large eggs
  • 6 Tablespoons unsweetened cocoa powder
  • 3/4 teaspoon baking powder
  • 1 teaspoon salt
  • 1 1/2 cups all-purpose flour
  • 1 Tablespoon vanilla extract
  • 1 ½ cups semi-sweet chocolate chips
Frosting + Decorations
  • 8 oz (one package) cream cheese, softened
  • 16 Tablespoons (two sticks) butter, softened
  • 6-7 c powdered sugar 
  • 2-4 Tablespoons milk
  • 1 T mint extract (I used McCormick’s Mint extract)
  • 1/4 t. salt (if using unsalted butter)
  • (Save and add later! 1-2 large drops Americolor Leaf Green – I used this to color about ½ cup of the frosting a deep green color that I loved! I added a tiny drop to another cup of frosting to make a mint green, and left the rest white.)
  • - Large piping bag & tip – I use this set of reusable large bags & tips more than almost any of my others! -
  • Small piping bag & tip – this set has been one of my favorites, and contains the small star and teardrop-tips I used to pipe the brownies in the photo/video!
  • Sprinkle mix of your choice! – I used ‘Silver Bells’ Sprinkle Mix by FancySprinkles, but any mix would work!
Preheat oven to 350°F. Grease a 9x13 baking pan with non-stick or baker’s floured cooking spray.
Mix together melted butter and granulated and brown sugars. Whisk in eggs until well combined. Whisk in cocoa powder, baking powder, salt, and gradually stir in all-purpose flour until combined. Stir in vanilla and chocolate chips, and pour into prepared pan.
Bake for 35-37 minutes (or until a toothpick comes out clean). Cool completely before frosting. Set in the fridge or freezer to accelerate the cooling process if desired.
This is a great time to make your frosting!
Frosting + Decorating
Color frosting to your liking, and transfer to piping bags – I used the large open star from my large tip set and a smaller open star and oblong teardrop-shaped tip from my smaller set when I piped the frosting onto the brownies – and I usually find it easiest to start with the larger tips and fill in around them with smaller designs. Up to you!
Add sprinkles to your liking – I started with larger ones spaced where I thought they looked best and then added smaller ones in between them. You could also skip the ‘placement’ and just sprinkle them over the top – either works but sometimes the second one’s more fun!
Annnd you’re done! High-five yourself –and enjoy!
  • Make this recipe? Let me know how it went - or find me on Pinterest or on Instagram and tag @IntensiveCakeUnit in your photo!