Found this handwritten on a recipe card in my grandmother’s recipe box dated 1972.

To stay true to the spirit of a 1970s Midwestern recipe card, this dish is intentionally simple, but there are many gentle ways to make it your own. For a slightly richer flavor, you can use Swiss or a mix of mozzarella and provolone in place of all mozzarella; Swiss will give you that classic, nutty casserole taste that many old Lombardy recipes used. If you prefer a bit of tang, sprinkle 2–3 tablespoons of grated Parmesan over the top along with the mozzarella.

You can also add 1/4 cup of dry white wine or chicken broth to the cream of mushroom soup before spreading it over the chicken for a looser, more sauce-like consistency and a little extra depth. For those who like onion, sauté a few tablespoons of finely chopped onion along with the mushrooms. If you need to watch sodium, choose a low-sodium cream of mushroom soup and go lighter on the salt, letting folks add more at the table.

For smaller households, this recipe halves easily; just use two chicken breasts and a smaller baking dish, keeping an eye on the baking time so the chicken doesn’t overcook. Leftovers keep well in the refrigerator for up to 3 days; reheat thoroughly until steaming hot before eating. For food safety, always start with fully thawed chicken, avoid rinsing raw chicken (it can spread bacteria around your sink), and wash your hands, cutting board, and knife well after handling it. Use a meat thermometer to confirm the chicken reaches 165°F (74°C) in the center before serving, and refrigerate any leftovers within 2 hours of cooking.