These are ridiculously good. I could even see chocolate icing on top. They remind me slightly of Reeses peanut butter cups.
If the butter is really room temperature these can be mixed by hand without a mixer.
1 stick of butter at room temperature
1/2 cup creamy peanut butter
1 cup light brown sugar
1/2 teaspoon vanilla
1 1/4 cup flour
2/3-3/4 cup semi sweet chocolate chips
Preheat the oven to 350 degrees. Cream the butter and peanut butter together. Add the sugar. Add the eggs and vanilla. Gradually add the flour and the finally the chocolate chips. Pour this into a prepared 8×8 pan and bake for 20-25 minutes or until a tooth pick inserted is removed clean.