1 cup butter, softened
1 1/2 cups white sugar
1 teaspoon vanilla extract
1 egg yolk
1/2 cup Irish cream liqueur
4 cups all-purpose flour
1/2 teaspoon salt
1 tablespoon baking powder
Cream together butter and sugar until fluffy. Beat in vanilla and egg yolk until combined, then beat in egg until smooth. Pour in Irish cream, and beat until mixed.
Sift together flour, salt, and baking powder. Stir into butter mixture until evenly mixed. Form into a flattened ball, wrap well with plastic wrap, and refrigerate 2 hours to overnight.
Preheat oven to 350 degrees F. Spray cookie sheet with non-stick cooking spray. Roll dough out to 1/4 inch thickness on a floured work surface. Cut into shapes using cookie cutters and place onto prepared baking sheets.
Bake in preheated oven until golden brown around the edges, 6 to 8 minutes. Cool on a wire rack until they reach room temperature.