1Heat oven to 350° F (325° F for dark or nonstick pan). Grease or spray bottom of 8-inch pan.
2Make brownie batter as directed on box, using water, oil, and eggs, adding cinnamon and chipotle powder until well blended. Spread into pan. Bake 39 to 42 minutes or until toothpick inserted 2 inches from edge comes out almost clean. Cool completely.
3In medium bowl, beat powdered sugar, dulce de leche, butter, milk, and vanilla with electric mixer on low speed until smooth and creamy. Spread onto cooled brownies.