In 2-quart saucepan, heat milk, chocolate chips, unsweetened chocolate and vanilla over low heat stirring constantly, until chocolate is melted and mixture is smooth; remove from heat. Gently spread over white chocolate layer. Sprinkle with 1/3 cup crushed cereal; press in gently. Sprinkle with powdered sugar. Refrigerate about 1 hour 30 minutes or until firm. Remove fudge from pan, using foil edges to lift. Cut into 8 rows by 6 rows. Store in plastic container with lid in refrigerator up to 2 weeks (place waxed paper or plastic wrap between layers and cover top layer before placing lid on top).