Preheat oven to 350°F. Line 8-inch square baking pan with aluminum foil, extending foil over sides of pan; lightly coat with nonstick cooking spray. Prepare brownies according to package directions. Stir in chilies; mix until well blended. Pour into prepared baking pan. Bake 25 to 30 minutes, or use time recommended on package. Cool on wire rack. Using foil “handles,” remove from pan. Blend powdered sugar and seasoning mix in small bowl. Stir in milk, adding more if necessary, until desired consistency. Spread on brownies. Slice and serve. Makes 9 servings.