1Heat oven to 350°F. Line 13x9-inch pan with foil, extending foil over 2 opposite sides of pan; spray with cooking spray. In 2-quart heavy saucepan, melt chocolates and butter over low heat, stirring constantly. Remove from heat; cool. In large bowl, beat sugar, eggs and vanilla with electric mixer on medium speed until thick and pale, about 5 minutes. On low speed, beat in flour, salt and melted chocolate until blended. Stir in marshmallows and peanuts. Pour into pan.
2Bake 35 to 40 minutes or until toothpick inserted in center comes out clean. Cool in pan on cooling rack, about 1 hour. Cover; refrigerate at least 2 hours. Use foil to lift out of pan. Cut into 6 rows by 3 rows. Insert stick into one end of each brownie. In small microwavable bowl, melt candy coating on High 30 to 45 seconds or until melted, stirring until smooth. Spoon into small resealable food-storage plastic bag; seal bag. Cut off tiny corner of bag. Drizzle over brownies. Sprinkle with pretzels. Let stand 30 minutes.