In a large bowl, on medium speed of an electric mixer, cream the butter until smooth. Add the sugar gradually and beat until fluffy, about 3 minutes. Add the eggs one at a time, beating well after each addition. Combine the flours and add in four parts, alternating with the milk and the vanilla extract, beating well after each addition. Spoon the batter into the cups about three-quarters full. Bake until the tops spring back when lightly touched, about 20 - 22 minutes. Remove cupcakes from pans and cool completely on a rack before icing.