Using a stand mixer or hand mixer, beat butter until creamy and light.
Reduce speed to low and add sifted cocoa powder. Beat until smooth and combined.
Reduce speed to low. Add powdered sugar 1 cup at a time mix on low until well blended. Increase speed to medium and beat for 3 minutes. Add vanilla and 2 Tbsp cream or milk and continue to beat on medium for 1 minute.
Add more cream /milk as needed until desired consistency is reached. Whip until the frosting is smooth and silky.