Philly-Style Chicken Cheese Steak
1 tablespoon butter 1 tablespoon olive oil 1 teaspoon seasoned salt 2 fresh hoagie rolls, split lengthwise 2 fresh mushrooms, sliced 2 skinless, boneless chicken breast halves 2 teaspoons mayonnaise, or to taste 4 leaves lettuce, shredded, or to taste 4 slices provolone cheese 4 slices tomato, or to taste ½ green bell pepper, sliced ½ large onion, sliced