For the frosting, beat butter and cream cheese for 3-5 minutes, until fluffy.
Beat in powdered sugar, cocoa powder, chocolate syrup and milk. Beat for an additional 3-5 minutes, adding more milk if needed to get desired consistency.
Use on cake or cupcakes, or spread over chocolate brownies.
Notes
Makes enough frosting for a 2 layer cake or 24 cupcakes.
If you want a tangier cream cheese frosting, increase cream cheese to 8 ounce. Skip the milk, and beat until smooth. It may be "softer" but perfect spread on cakes!
Store in refrigerator for up to 5 days. If too hard to spread, beat with mixer again before using.