Idaho Potato Vegetable Casserole Supreme

Name: Idaho Potato Vegetable Casserole Supreme
Prep time: 15 min
Cook time: 45 min
Total time: 1 h
Cuisine: American
Ingredients: 1 (10 oz.) bag microwavable frozen mixed steamed vegetables (peas, carrots, green beans, corn); 8 Tablespoons unsalted butter (, divided); 1 small yellow onion (chopped); 2 lb bag frozen diced hash brown potatoes (, thawed); 1 (10.75 oz) can cream of chicken soup; 2 cups shredded sharp cheddar cheese; 1 cup sour cream; 2 teaspoons salt; 1 teaspoon pepper; 1 sleeve Ritz crackers (, crushed)