01 - Preheat oven to 350°F. Grease and line a 9x13-inch baking pan with parchment paper.
02 - In a large mixing bowl, whisk together melted butter, granulated sugar, and brown sugar until well combined. Add eggs one at a time, mixing well after each addition. Stir in vanilla extract.
03 - In a separate bowl, sift together flour, cocoa powder, baking powder, and salt.
04 - Gradually fold dry ingredients into wet mixture until just combined. Do not overmix the batter.
05 - Pour batter into prepared pan and smooth the top with a spatula. Bake for 22 to 25 minutes until a toothpick inserted in the center comes out with a few moist crumbs. Cool completely in the pan.
06 - Beat softened butter until creamy. Gradually add powdered sugar, mixing on low speed. Add milk, vanilla extract, salt, and pink food coloring. Beat on high speed until frosting is fluffy and evenly colored.
07 - Once brownies have cooled completely, lift them out of the pan and place on a cutting board. Use a heart-shaped cookie cutter to cut out individual brownie hearts.
08 - Spread or pipe pink frosting onto each heart-shaped brownie. Add sprinkles or additional decorations as desired.