In a large bowl, combine the crumbs, peanuts, sugar and peanut butter until crumbly. In a small saucepan, melt the chocolate chips and milk over low heat, stirring constantly until smooth. Remove from the heat; add vanilla. Set aside 1/2 cup.
Pour remaining chocolate mixture over crumb mixture and stir until well blended. Spread evenly in a greased 9-in. square dish. Frost with the reserved chocolate mixture. Cover and refrigerate for 1 hour.