In a medium bowl, combine white and brown sugar. Mix well. Add the softened butter and using the electric mixer, cream well until smooth.
Remove from the oven and let cool on the baking sheet for 5 - 7 minutes. Transfer to the wire rack to cool completely.
In a separate bowl, sift flour, baking powder, baking soda, and salt; Add into the wet mixture and mix well until combined.
Roll dough into 1 inch balls and place on the baking sheets.
Flatten each ball with a fork, making a crisscross pattern.
Bake for about 11 minutes or until cookies start turning light brown on the edges.
Enjoy the soft and chewy peanut butter cookies with milk.