Prep:15min › Cook:5min › Extra time:1hr › Ready in:1hr20min
Melt butter in a medium saucepan over medium heat. Stir in brown sugar and milk. Bring to the boil and boil for 2 minutes, stirring frequently. Remove from heat. Stir in peanut butter and vanilla. Pour over icing sugar in a large mixing bowl. Beat until smooth; pour into a 20cm square baking dish. Chill until firm and cut into squares.