Cream butter and brown sugar for 3 minutes, until it is light and fluffy.
Add the egg and vanilla.
Mix in flour, baking powder, and salt.
Add the Snickers pieces.
Add the batter to an 8×8 inch pan that has been lined with tin foil or parchment paper. The overhang makes it so much easier to get the bars out of the pan. Spray lightly with cooking spray.
Bake in a preheated 350 degree oven for 25 to 30 minutes. Cool and cut into 16 squares.