Reciprocal Cookies (Chocolate)

This is an old recipe from the King Arthur 200th Anniversary Cookbook. I’ve made these cookies many times. Typically I make only the the chocolate cookies with peanut butter chips, but I love the math reference in the recipe title!


  • ½ cup (1 stick) butter
  • ½ cup sugar
  • ½ cup brown sugar
  • 1 egg
  • 2 squares (2 ounces) unsweetened baking chocolate melted
  • 1 teaspoon vanilla
  • 1¼ cups (162 grams) unbleached all-purpose flour
  • ½ teaspoon baking soda
  • ¼ teaspoon salt
  • 1 cup peanut butter chips


  1. Cream the butter and sugars until light. Beat in the egg, melted chocolate and vanilla. Mix the flour, baking soda and salt together and add to the butter mixture. Blend in the peanut butter chips. Cover the dough and chill for an hour.
  2. Preheat the oven to 375°F.
  3. Drop by teaspoonfuls on a lightly greased cookie sheet and bake for 10 to 12 minutes.