Cream together butter, sugar and vanilla in a mixer.
Add flour, baking powder and salt.
Mix together well.
Divide dough in three equal portions.
Roll each portion into about an 8" long roll. Use flour on your surface when doing this to prevent sticking.
Cover (I use wax paper) and refrigerate.
After about an hour or longer, when dough is firm, slice each roll into about 15-20 slices.
Take each sliced, unbaked cookie and press one side into sprinkles.
On a lightly greased cookie sheet, bake at 350 degrees for about 10 minutes, before they brown. (Edges may brown slightly but they should look almost undone.)
Cool and enjoy!