Preheat your oven to 350°F (175°C). Grease and flour a 9×13 inch baking pan, or line with parchment paper, leaving an overhang on the sides.
In a large bowl, combine the melted butter and granulated sugar. Whisk until well combined.
Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
In a separate bowl, whisk together the flour, cocoa powder, baking powder, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix.
Pour the brownie batter into the prepared baking pan and spread evenly.
Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with moist crumbs, but not wet batter.
Remove the brownies from the oven and let them cool completely in the pan on a wire rack.
While the brownies cool, prepare the fudge ganache. In a small saucepan, heat the heavy cream over medium heat until it just begins to simmer. Remove from heat.
Add the chocolate chips and butter to the hot cream. Let sit for 5 minutes, then whisk until smooth and glossy.
Once the brownies are completely cool, pour the ganache over the top and spread evenly with an offset spatula.
Immediately sprinkle the candy-coated chocolate sprinkles over the wet ganache, pressing them gently to adhere.
Allow the ganache to set at room temperature for at least 30 minutes, or refrigerate for 15-20 minutes, before cutting into squares and serving.