Preheat oven to 350° F.
Combine flour, baking powder, and salt in a medium bowl. (For chocolate chip whoopie pies, add 1/2 cup chocolate chips to dry ingredients).
In another large bowl, cream together butter, sugar, eggs, and vanilla.
Slowly add milk and mix well. Sift dry ingredients into creamed mixture.
Drop batter by the teaspoon on parchment lined cookie sheets, about 2 inches apart, and bake for 10 minutes, or until springy to the touch.
Cool on baking sheets for 5 minutes, then place on wire racks to cool completely.