Line 2 baking sheets with parchment paper and preheat the oven to 350 degrees F.
Sift the flour, baking powder and salt together.
In a mixing bowl with the paddle attachment, cream the butter and sugars on high speed. Add the eggs on low speed, followed by the Irish cream. Then slowly add the flour mixture. Add the white chocolate chips.
Using a 2-tablespoon scoop, portion the dough onto a parchment-lined sheet pan. Space the cookies at least 1 1/2 inches apart (you may need to cook them in batches).
Chill for 15 minutes or longer, then bake for 13-15 minutes. Allow to cool for 5 minutes before transferring to a cooling rack. Store leftover cookies in an airtight container for up to 7 days (they'll be best within the first 3-4 days).