I found this recipe at Food Network Canada courtesy of Anna Olson.
½ cup unsalted butter, room temperature
½ cup sugar
½ cup brown sugar
1 tsp vanilla extract
½ cup peanut butter (smooth or crunchy)
1 ½ cup all purpose flour
1 tsp baking soda
¼ tsp salt
1. Preheat oven to 350° F. Cream together butter and sugars until pale and fluffy. Beat in egg and vanilla. Stir in peanut butter. In a separate bowl, combine flour, baking soda and salt. Add to peanut butter mixture and blend in. Drop by tablespoonfuls onto an ungreased cookie sheet and crisscross mark them with a floured fork. Bake for 9 to 11 minutes, until cookies just start to colour around the edges.
2. Yield: 2 dozen cookies