In a mixing bowl with an electric mixer, beat the softened butter and vanilla until creamy. Slowly beat in confectioners’ sugar and about 3 tablespoons of the Irish cream.
Continue beating on medium speed, adding more Irish cream, a teaspoon or two at a time, until the desired consistency is reached. Spread or pipe on a cake or cupcakes.
Makes enough for a two-layer cake or about 1 1/2 dozen cupcakes.