Lentil Soup with Spicy Italian Sausage

Name: Lentil Soup with Spicy Italian Sausage
Ingredients: 2 tablespoons olive oil; 1 pound fully cooked hot Italian sausage, cut into 1/2-inch cubes; 1 large onion, chopped (about 3 cups); 2 large carrots, peeled, chopped (about 1 3/4 cups); 2 large parsnips, peeled, chopped (about 1 3/4 cups); 2 large celery stalks, chopped (about 1 cup); 2 1/2 teaspoons dried Italian seasoning blend; 1 pound brown lentils (about 2 1/3 cups); 3 quarts (or more) low-salt chicken broth; 1 5-ounce package baby spinach leaves