Farmhouse Harvest Soup with White Beans

Name: Farmhouse Harvest Soup with White Beans
Cuisine: American, Southern
Ingredients: 2 tablespoons olive oil; 1 large leek (sliced (about 1 3/4 cups)); 1 onion (finely chopped (1 ½ cups)); 1/2 cup chopped carrots; 2 cups chopped celery (3 - 4 stalks); 2 cups chopped butternut squash; 1 Serrano pepper (minced (1 1/2 - 2 tablespoons)); 2 garlic cloves (minced); 2 tablespoons fresh thyme; 1 teaspoon dried oregano; 2 teaspoons kosher salt (or 1 teaspoon table salt); 10 twists of freshly ground pepper; 8 cups vegetable broth; 2 chunks of the rind of Parmesan cheese; 3 cups cooked white beans; 1 1/2 cups roasted chicken, (optional); 5 tablespoons harissa; 1 bunch spinach (stemmed); 4 large tomatoes (a mix of red and yellow)