Turkey Sweet Potato Shepherds Pie

Name: Turkey Sweet Potato Shepherd's Pie
Ingredients: 2 tablespoons extra-virgin olive oil; 2 pounds ground turkey or chopped leftover turkey; Salt and freshly ground black pepper; 2 teaspoons poultry seasoning; 2 1/2 pounds sweet potatoes, peeled and cubed; 1 onion, cut into 1-inch dice; 2 carrots, peeled and grated; 4 ribs celery, chopped; 4 tablespoons butter, divided; 2 tablespoons flour; 2 cups turkey or chicken stock (recommended: Kitchen Basics brand); A few dashes Worcestershire sauce; 1 (10-ounce) box frozen peas; 1 very ripe banana; A few dashes hot sauce; 2 cups shredded sharp yellow Cheddar