1 cup butter, plus more for greasing pan
1 1/4 cup peanut butter
1 teaspoon pure vanilla extract
1 pound confectioner sugar
Heat peanut butter and butter in double boiler until thoroughly mixed and heated through. Add vanilla and confectioner sugar to peanut butter mixture and stir to combine with a wooden spoon. Remove from heat. Pour into a buttered 8×8 or 9×9 pan lined with waxed paper. Place a second piece of waxed paper on the surface of the fudge and refrigerate until cool. Cut into 1-inch pieces and store in an airtight container for up to a week.
Note: Alternately, you can microwave butter and peanut butter for 2 minutes on high. Stir and microwave on high for 2 more minutes before adding the sugar and vanilla.