1. Preheat the oven to 350 degrees and grease an 8x8 baking pan.
2. Whisk together the flour, baking powder, baking soda, and salt.
3. Beat together the butter, peanut butter, and brown sugar.
4. Add the egg and vanilla.
5. Add the dry ingredients and mix.
6. Press the dough into the prepared pan and sprinkle the sugar on top.
7. Bake for 20 to 25 minutes.
8. Immediately after removing the pan from the oven, press the Kisses into the bars.
9. When the dough has cooled completely, cut into bars and serve.