Cream together butter, peanut butter and sugars. Beat in eggs.
In a separate bowl, sift together flour, baking powder, baking soda, and salt. Stir into batter. Put batter in refrigerator for 1 hour.
Press dough on to a baking sheet. (I use a large deep cookie sheet) Flatten. Bake in a preheated 375 degrees oven for about 15 minutes or until cookies begin to brown. Do not over-bake. Cool, and cut into bars. Optional: Remove pan from oven, and sprinkle with chocolate chips. Let stand 5 minutes and spread evenly over bars. Cool, and cut into bars.
You can also use this to do regular cookies, follow steps 1 and 2 and then Roll into 1 inch balls and put on baking sheets. Flatten each ball with a fork, making a criss-cross pattern. Bake in a preheated 375 degrees F oven for about 10 minutes or until cookies begin to brown. Do not over-bake. (MAKES ABOUT 4 DOZEN)