Preheat oven to 325°F. Spray a 9x9-inch baking pan with nonstick spray and line it with parchment paper. Set aside.
In a medium bowl, whisk the flour and cocoa powder together.
¾ cup all-purpose flour, ⅔ cup unsweetened cocoa powder
In a separate larger bowl, whisk the butter and sugars together.
12 tablespoons unsalted butter, 1 cup granulated sugar, ½ cup brown sugar
Add in the eggs, vanilla extract, and salt.
2 large eggs, 1 teaspoon pure vanilla extract, ¾ teaspoon kosher salt
Add the flour mixture to the wet ingredients and stir until just combined. Do not overmix the batter; otherwise, your brownies may come out tough.
Pour the batter into the pan, and use a spatula to spread it out.
Bake for 30-35 minutes, or until a toothpick comes out nearly clean. Allow brownies to cool.
While the brownies are baking, place 1/2 cup of heavy cream in a pot and add 1 cup of chocolate chips. Heat, stirring until the chocolate is melted and smooth.
1 cup chocolate chips, ½ cup heavy cream
Spread the frosting out over the brownies. Then, sprinkle rainbow chips over the frosting.
¼ cup rainbow candy-coated chocolate chips
Refrigerate or freeze to let the frosting set before enjoying!