Garden Vegetable Soup

Ingredients

2 tablespoons olive oil or butter
2 cups diced onions
1 1/2 cups diced carrots
1 1/2 cups small-diced celery (with or without leaves)
2 tablespoons minced garlic
8 ounces button mushrooms, wiped clean, stemmed, and quartered (about 2 cups)
6 sprigs parsley
4 quarts beef, chicken, or vegetable stock or canned, low-sodium beef, chicken, or vegetable broth [3]
1 1/2 teaspoons salt
3/4 teaspoon freshly ground black pepper
2 cups broccoli or cauliflower florets, cut into bite-size pieces
1 cup diced zucchini (large dice)
1 cup diced yellow squash (large dice)
1/2 cup grated Parmigiano-Reggiano cheese (optional)

Heat olive oil in a 6-quart or larger soup pot over high heat. Add onions, carrots, and celery and cook for 2 minutes, stirring frequently. Add garlic, mushrooms, and parsley and cook for 3 minutes. Add stock, salt, and pepper. Cover and bring to a boil. Remove cover, reduce the heat to medium-low, and simmer for 12 minutes.
Add broccoli, zucchini, and yellow squash. Simmer 5 minutes.
Remove parsley sprigs and serve soup hot, garnished with the grated cheese, if desired.