1 tablespoon olive oil 12 ounces mild italian sausage (remove f 1/2 red onion, diced 1 leek, chopped (white and light green parts only) 1/2 cup chopped carrots, about 1 medium 1/2 cup diced celery, about 2 ribs 1 small zucchini, chopped 3 cloves garlic, minced 1 tablespoon tomato paste 1 tablespoon italian herb blend 1