Irish cream by itself can be pretty strong. Since I am out of vanilla ice cream to make shakes, I mixed some 2% milk in with some, and it was pretty good. So I measured out a controlled group and came up with the following:

1/2 cup of Irish Cream (Bailey's, Emmets, Cask & Ale, ect)
1-1/2 cups of 2% milk

Stir and drink.