Combine butter, marshmallows and chocolate in a 2 litre saucepan. Cook over low heat, stirring constantly, until melted and well blended. Remove from heat. Gradually add flour and salt, mixing well. Stir in vanilla and peanuts. Pour over popcorn, mixing well. Press into well greased 13x9 inch pan. Bake at 180ºC or 10 to dozen minutes. Cool; cut into bars. Dust with confectioners sugar, if desired. Mrs. Mildred Larson, Chicago Ill.