Cheesy Potato with broth

1/4 cup butter 1/2 stick, or half olive oil and half butter 1 pound mushrooms white or cremini, sliced 1 tablespoon garlic minced 4 cups leeks thinly sliced[...]

2 1/2 lbs potatoes , peeled and sliced thin 1 medium onion , diced 2 -3 cups cooked chicken, diced (or other leftover cooked meat) 2 cups cheddar cheese ,[...]

4 (14 1/2 ounce) cans reduced-sodium chicken broth 3 cups heavy cream 2 cups Simply Potatoes Traditional Mashed Potatoes 16 ounces shredded monterey jack[...]