Basic Vegetable Stock

Name: Basic Vegetable Stock
Ingredients: 1 large onion; 2 large carrots; 2 celery ribs, including a few leaves; 1 bunch scallions, including half of the greens; 1 tablespoon olive or vegetable oil; 1 tablespoon nutritional yeast, optional; 8 garlic cloves, peeled and smashed; 8 parsley branches; 6 thyme sprigs or ½ teaspoon dried; 2 bay leaves; Salt