2 tablespoons unsalted butter
1 tablespoon olive oil
1 red onion, diced
2 shallots, thinly sliced
1 red bell pepper, cored, seeded, and diced
3 ribs celery, diced
6 garlic cloves, minced
8 cups chicken broth
4 cups shredded cooked chicken
2 sweet potatoes, peeled and chopped into 1/2-inch chunks
One 14 1/2-ounce can chopped tomatoes
1/2 teaspoon red pepper flakes
1 teaspoon dried marjoram
3 bay leaves
2 teaspoons salt
1 teaspoon freshly ground black pepper
1 tablespoon chopped fresh marjoram, to garnish, optional
1 tablespoon chopped fresh thyme, to garnish, optional
Salt and freshly ground pepper to taste
1. Melt the butter and olive oil over medium-low heat in a large saucepan and add the onion and shallots. Cook and stir about 15 minutes, or until softened. Add the bell pepper and celery and continue to cook and stir about 5 minutes longer. Add the garlic and cook and stir 2 to 3 minutes longer.
2. Add the broth, chicken, sweet potatoes, tomatoes, red pepper flakes, dried marjoram, bay leaves, salt and pepper and stir until combined. Bring to a low boil, reduce heat, and simmer, uncovered, about 1 hour, until the potatoes are tender and flavors have developed. Skim the top of the soup as it cooks if necessary to remove foam or fat.
3. Discard the bay leaves. Add the fresh marjoram, thyme, and additional salt and pepper if desired. Serve immediately.