Preheat your oven to 350F.

Spray 8x8 baking pan with nonstick baking spray and line the bottom with parchment paper.

Pour melted butter into a medium bowl, then whisk in granulated sugar and light brown sugar until combined.

Mix in the vanilla extract, then whisk in the eggs, one at a time. Whisk mixture vigorously until thick and golden, then set aside.

In a small bowl, whisk together the flour, baking powder, and salt.

Use a spatural to fold the flour mixture into the wet mixture until all ingredients are just combined.

Fold in the ½ cup sprinkles and the ½ cup mini chocolate chips until evenly distributed throughout the batter.

Pour batter into prepared baking pan and bake at 350F for 35-40 minutes, then remove pan to a cooling rack. Let blondies cool completely before removing from pan and covering with ganache.

While the blondies bake, make the ganache.

Place 8 oz chocolate chips/pieces in a heat-resistant bowl. Set aside.

Pour heavy cream and kosher salt into a small saucepan and bring to a boil over medium-low heat, about 7-8 minutes.

Remove saucepan from heat and pour the hot cream over the chocolate chips, jiggling the bowl a little so all chips are covered by the cream. Let stand one minute.

Use a small spatula to gently stir the chips into the cream until the chocolate and cream are thoroughly combined and the ganache is smooth and thick.

Cover the ganache with plastic wrap and let cool for about 30 minutes. Ganache should be thick but pourable.

Pour ganache over cooled blondies in desired amount, then garnish with more rainbow sprinkles and mini chocolate chips. Let ganache harden before cutting and serving the blondies.