Heat olive oil over medium heat in a large (4-quart) pot. Add onion and carrots, and saute (cook while stirring occasionally) until softened, 8 to 10 minutes. (Adjust heat to medium-low if onion is browning too quickly). Add sausage, ¼ teaspoon salt and 1/8 teaspoon pepper and cook until sausage begins to brown, 5 to 10 minutes. Stir in garlic and cook, 1 to 2 minutes. Add beans, canned tomatoes, 3 cups broth, barley, Swiss chard stems and thyme; bring to a simmer and cook, uncovered, for 10 minutes, stirring occasionally. Add Swiss chard leaves and continue to cook, uncovered, until chard leaves are wilted and barley is tender, 3 to 5 minutes. If you like a more saucy stew, add up to a cup of additional chicken broth to desired consistency. Season with salt and pepper to taste. Serve with lemon wedges for squeezing and a sprinkle of Parmesan cheese.