Preheat the oven to 350 degrees F. In a large mixing bowl, cream the butter, peanut butter, brown sugar, and sugar until well blended. Beat in the egg, milk, and vanilla. In a separate bowl, combine the flour, baking powder, and salt. Gradually add the dry ingredients to the creamed mixture. Stir in the chocolate chips and peanuts. Chill the dough in the refrigerator for 15 minutes. Drop heaping tablespoons of dough onto an ungreased cookie sheet.
Bake 12 to 14 minutes, or until the edges are golden brown. Cool 1 minute on cookie sheet, then transfer to wire cooling racks. Store tightly covered.