Ingredients:

  • 8 Tbsp (1 stick) Unsalted Butter, cubed
  • 4 oz Dark Chocolate (70% cacao), finely chopped or chips
  • 1 cup Granulated Sugar
  • ½ cup Light Brown Sugar, packed
  • 3 Large Eggs, at room temperature
  • 1 tsp Vanilla Extract (for brownie)
  • ¾ cup All-Purpose Flour
  • ¼ cup Unsweetened Cocoa Powder (Dutch Process)
  • ½ tsp Fine Sea Salt (for brownie)
  • ½ cup Rainbow Sprinkles (Jimmies style, for brownie)
  • 1 cup (2 sticks) Unsalted Butter, softened (for frosting)
  • 3 cups Powdered Sugar (Icing Sugar), sifted
  • 2-3 Tbsp Heavy Cream or Whole Milk
  • 1 tsp Vanilla Extract (for frosting)
  • Pinch of Salt (for frosting)
  • ¼ cup Rainbow Sprinkles (for folding in frosting)

Instructions:

  1. Prep and Preheat: Preheat oven to 350°F (175°C). Line a standard 12-cup muffin tin with paper liners.
  2. Melt the Base: Combine the butter and chopped dark chocolate in a heatproof bowl set over a simmering pot of water. Stir until completely smooth and glossy. Remove from heat and let cool slightly (about 5 minutes).
  3. Whip the Sugars: Whisk the granulated sugar and brown sugar into the slightly cooled chocolate mixture.
  4. Incorporate Eggs: Vigorously whisk the eggs in one at a time, followed by the vanilla extract. Whisking for about 60 seconds after the final egg is added helps develop the classic shiny, crackly brownie crust.
  5. Add Dry Ingredients: In a separate bowl, whisk together the flour, cocoa powder, and salt. Gently fold the dry ingredients into the wet mixture using a spatula until just combined. Stop mixing as soon as no dry streaks remain.
  6. Fold in Funfetti: Gently fold in the ½ cup of rainbow sprinkles.
  7. Portion and Bake: Scoop the batter evenly into the lined muffin cups, filling them about two-thirds full.
  8. Bake: Bake for 22–25 minutes at 350°F (175°C). A toothpick inserted into the center should come out with moist, fudgy crumbs attached (not clean).
  9. Cool: Transfer the cupcakes to a wire rack immediately to cool completely before frosting (approximately 45 minutes).
  10. Cream Butter: Using an electric mixer, beat the softened butter until light and fluffy (3–5 minutes).
  11. Add Sugar: Gradually add the sifted powdered sugar, alternating with the heavy cream and vanilla. Mix on low speed until combined, then ramp up to medium-high. Beat until the frosting is light, smooth, and spreadable. Add the pinch of salt.
  12. Fold in Sprinkles: Gently fold the remaining ¼ cup of sprinkles into the finished buttercream.
  13. Decorate: Once the brownie cupcakes are completely cool, pipe or spread the frosting generously onto each top.
  14. Final Flourish: Scatter a few extra sprinkles over the top for maximum visual appeal before serving.