Peanut Butter Fudge

1 cup butter
1 cup peanut butter
1 tsp vanilla extract
1 pound powdered sugar

Microwave butter and peanut butter for 2 minutes on high.  Stir and microwave on high for 2 more minutes.  Add vanilla extract and powdered sugar.  Stir with a wooden spoon.  Pour into a buttered 8 by 8 inch pan lined with wax 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.