Creamy Potato and Corn Chowder

Name: Creamy Potato and Corn Chowder
Ingredients: 2 tablespoons butter or olive oil; 1 cup chopped celery; 1 cup chopped onion; 2 cloves garlic (minced); 32 oz chicken broth; 4 cups peeled and diced potatoes; 2 cups whole kernel corn (fresh, frozen, or canned); 1 cup diced ham (or 1/4 cup cooked, diced bacon); 4 oz can diced green chile; 2 cups whole milk; 2.5 oz package of country gravy mix; Salt and black pepper to taste; 1 cup shredded cheddar cheese; Optional: Cheese, (green onions, or bacon bits for garnish.)