Combine the first 3 ingredients in a small saucepan; stir over low heat until melted and smooth. Spread onto the bottom of a lightly greased 13 x 9 x 2 in. pan. Refrigerate until set.
For filling: Melt butter in a heavy saucepan over medium-high heat. Add sugar and milk. Bring to a boil; boil and stir for 5 min. Remove from heat; stir in the marshmallow cream, peanut butter and vanilla. Add peanuts. Spread over first layer. Refrigerate until set.
Carmel Layer: Combine caramels and cream in a saucepan; stir over low heat until melted and smooth. Spread over the filling. Refrigerate until set.
Icing: In another saucepan, combine chips and peanut butter; stir over low heat until melted and smooth. Pour over the caramel layer. Refrigerate for at least 1 hour. Cut into 1 in. squares. Store in the refrigerator.