Cosmic Brownie Cookies - soft, fudgy chocolate cookie base topped with a rich and decadent homemade chocolate buttercream with fun rainbow chips. It's nostalgia in a cookie!
In a large bowl cream together the butter and both sugars until fluffy.
½ cup unsalted butter, ¾ cup light brown sugar, ¼ cup granulated white sugar
Beat in the egg, vanilla extract, and cocoa powder.
1 large egg, 1 teaspoon vanilla extract, ¼ cup unsweetened cocoa powder
Add in the flour, salt, and baking powder. Mix until just combined. It will be very crumbly but should easily press together.
2 cups all purpose flour, ½ teaspoon salt, ½ teaspoon baking powder
Divide the dough into 6 equal portions and form each portion into a large ball.
Place the balls onto a baking sheet lined with parchment paper or a silicone baking mat. Loosely cover with plastic wrap and refrigerate for at least 30 minutes.
While chilling, I suggest making the buttercream and preheating the oven to 350°.
Once chilled, bake the cookies for 15-18 minutes. The edges should be just golden. If you over-bake, you'll lose the chewiness. Press down with the back of a spatula if you prefer flatter cookies.
Cool 5 minutes and then transfer to a rack to cool completely.
To make the chocolate buttercream
To a medium microwave safe bowl, add the chocolate and heat in 30 second increments, stirring in between, until melted and smooth. Cool 5 minutes.
2 ounces unsweetened baking chocolate
Once cooled, add the softened butter, vanilla extract, and powdered sugar. Use a hand mixer to beat until smooth.
Gradually add the milk while beating with the mixer until the desired consistency is reached.
3.5 Tablespoons milk
Taste and adjust to your preference. I add an additional pinch of salt because I don't like overly sweet buttercream.
1 pinch salt
Transfer the frosting to either a piping bag fitted with a large, round tip OR place it into a large zip top bag and snip the tip.
Assemble
Pipe the buttercream into a swirl on top of the cooled cookies. (alternatively, you can simply frost them with an offset spatula).
Sprinkle with rainbow chips and enjoy!
Rainbow candy chips
Notes
You can use a zip top bag with the tip cut off if you don't have a piping bag. Or, just frost the cookies with a knife.
You can find the rainbow chips on Amazon, but I have found them at craft stores(I got mine at Hobby Lobby).
You must refrigerate the cookies before baking to keep them nice and tall and chewy.
Gently press the cookies down with a spatula when they come out of the oven if they don't spread enough.
You can add some rainbow chips or regular chocolate chips to the dough for an extra dose of chocolate.
This recipe makes 6 LARGE cookies. They're big enough to share. You can either double the recipe to make more, or just divide the dough into smaller portions.
Store leftovers in an airtight container at room temperature for up to 3 days.