Melt butter in a medium saucepan over medium heat.
Stir in brown sugar and milk.
Bring to a hard, rolling boil then continue to 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.
Servings: 15 (from 8"x8" pan)
Tip:
Line the pan with plastic wrap before pouring in the fudge. When the fudge has cooled, you can just pop it out of the pan and peel off the plastic wrap - no sticky pan to clean!