Preheat oven to 350 degrees. Line muffin tin with paper liners, set aside.

In the bowl of your stand mixer whisk - using a whisk or even the whisk attachment - the flour, sugar, baking powder and salt together very well. Change to the paddle attachment and beat softened butter, sour cream, egg, egg yolks and vanilla on medium speed until just combined and smooth. Do not over-mix! Fold in sprinkles by hand. Distribute batter evenly into liners abut ⅔ full. Do not go any higher than that or they will spill over the sides. Bake for 18-22 minutes or until the tops spring back and a toothpick inserted into the center comes out clean. Allow to cool in the pan for 5 minutes or until cool enough to handle and transfer to wire rack to finish cooling completely before frosting them.

For the frosting, cream butter and Nutella together until smooth and no lumps remain. Add cocoa and confectioner's sugar and beat again until smooth. Add heavy cream one tablespoon at a time until your desired consistency is achieved. Once cupcakes are completely cool, go ahead and frost them.

Homemade Funfetti Cupcakes With Nutella Frosting will stay fresh for up to 4 days stored in an airtight container at room temperature.