1/3 cup Bailey's Irish Cream (the original recipe calls for 2/3 heavy cream and no Bailey's in the filling, but I found it increased the awesome quotient just a little bit)
2 tablespoons butter, room temperature
1 to 2 teaspoons Irish whiskey
For the frosting
Note: If you want lots of frosting on each cake, go ahead and double this recipe
3 to 4 cups confections' sugar
1 stick (1/2 cup) unsalted butter, at room temperature
3 to 4 tablespoons Bailey's Irish Cream (or more, to taste)