Peanut Butter Fudge

1 stick butter
2 1/4 c brown sugar
1/2 c milk
3/4 c peanut butter
1 tsp vanilla extract
3 1/2 c powdered sugar

Melt butter in a medium saucepan over medium heat. Stir in brown sugar and milk. Bring to a boil and boil for 2 minutes, stirring frequently. Remove from heat. Stir in peanut butter and vanilla. Pour over powdered sugar in a large mixing bowl. Beat until smooth; pour into an 8x8 inch dish. Chill until firm and cut into squares.