In a large bowl, use an electric mixer to cream together the butter and cream cheese until smooth and well- combined. Add the sugar and vanilla and and continue beating until of spreading consistency. Add a drizzle of milk or cream, if needed, to thin out the frosting (for a thinner spreading consistency).
Frost your cake or cupcakes and keep refrigerated.
This recipe makes enough to frost 24 cupcakes or a two-layer cake.