In a stand mixer, fitted with a paddle attachment, cream the butter first until light and fluffy on medium-high speed, for about 1 minute. 10 Tablespoons (1 1/4 sticks, 141 g) unsalted butter
With the mixer on low speed, slowly add in the in the powdered sugar, ¼ cup at a time. And then once incorporated, mix on medium-high sped for about 1 to 2 minutes until light and fluffy. 1 ¼ cups (141 g) powdered sugar
With ther mixer on low, add the vanilla extract and heavy cream. Mix on low to combine. 1 Tablespoons heavy cream 1 teaspoons vanilla extract
Add in the cocoa powder and mix on low speed at first until incorporated. 6 Tablespoons (32 g) unsweetened cocoa powder or Dutch Process
Increase the speed to medium-high speed and mix for 8 minutes until light and fluffy. Scrape down the bowl as needed. Use right away, or store in the fridge, in a covered container for up to 5 days.
Spread the frosting on the top and sides of the cooled cake. Top with sprinkles