In a large stockpot over medium heat melt 1 tablespoon of unsalted butter, add chopped onions and sauté until tender. Add minced garlic, diced carrots, and celery, sauté until tender. Season with kosher salt and freshly ground black pepper to taste, or begin with 1 teaspoon each, adjust as needed.
Add fresh baby spinach and chicken stock, stir well. Increase heat and bring stock to a rolling boil. Once stock is boiling add tortellini, reduce heat to medium high, stir pasta. Cook tortellini according to package instructions. Adjust seasonings, top with chopped fresh parsley, a sprinkle of parmesan cheese and serve.