Winter Root Vegetable Soup

Name: Winter Root Vegetable Soup
Ingredients: 3 parsnips, peeled and cut into 1/2-inch pieces; 3 carrots, peeled and cut into 1/2-inch pieces; 1 celery root, peeled and cut into 1/2-inch pieces; 2 turnips, quartered; 1 sweet potato, peeled and cut into 1/2-inch pieces; 1 (2 pound) butternut squash, peeled and cut into 1/2-inch pieces; 0.25 cup olive oil; 1 teaspoon kosher salt; 0.5 teaspoon ground black pepper; 3 tablespoons butter; 1 stalk celery, diced; 0.5 sweet onion, diced; 1 quart vegetable broth; 0.5 cup half-and-half cream; salt and ground black pepper to taste