Try to use the best quality cocoa powder possible to enrich the chocolate flavoring. The best option in most grocery stores is Ghirardelli Sweet Ground Cocoa
FAVORITE CHOCOLATE BUTTERCREAM
INGREDIENTS
1 cup unsalted butter, softened
3 1/2 cups powdered sugar, sifted
1 teaspoon vanilla extract
1 cup cocoa powder, sifted
2-3 tablespoons milk
DIRECTIONS
In the bowl of an electric stand mixer with a paddle attachment, cream the butter until light and fluffy (about 5 minutes). Scrape sides and bottom of bowl
Beat in vanilla and milk
Increase mixer speed to low-medium (setting 4 on most KitchenAid mixers) and slowly add cocoa powder and powdered sugar until incorporated
Increase mixer speed again to medium-high (setting 6 on most KitchenAid mixers) and continue beating for 5-8 minutes until frosting is light and creamy