Cheesy Chicken Philly Skillet

Name: Cheesy Chicken Philly Skillet
Ingredients: 1 tablespoon oil; 1 package (20 oz) boneless skinless chicken breasts, cut into 3/4-inch pieces; 1 package (8 oz) sliced baby portabella mushrooms; 1 medium red bell pepper, chopped (1 cup); 1/2 cup chopped onion; 1 1/4 cups milk; 3/4 cup hot water; 1 box Hamburger Helper™ Philly cheesesteak; 1/4 teaspoon crushed red pepper flakes; 1 cup shredded mozzarella and provolone cheese blend (4 oz)