Sweet Potato and Apple Soup

Name: Sweet Potato and Apple Soup
Ingredients: 3 tablespoons extra-virgin olive oil; 2 leeks, whites only, cleaned and sliced thinly; 2 stalks celery, sliced thinly; 3 large sweet potatoes (larger than a fist), peeled and cut into large dice; 1 tart green apple, peeled, cored, and diced; 7 cups chicken or vegetable stock; 1 dried bay leaf; 1 teaspoon fresh thyme leaves; ¼ teaspoon ground cinnamon; ½ teaspoon curry powder; ½ cup half-and-half or light cream; Salt and freshly ground black pepper to taste; ½ cup freshly squeezed orange juice; Extra thyme leaves for garnish