Heat a medium saucepan over medium heat for 2-3 minutes. Add the oil. When it shimmers, add the onion and garlic (if using). Season with a pinch of salt and pepper. Sweat for 5 minutes until translucent. Add the sausage and break up well with a spoon or spatula. Cook until the sausage is browned, about 5 minutes. Stir in the Italian seasoning. Pour in the tomato puree (or pureed tomatoes), the broth or water and the chickpeas. Season to taste with salt and pepper. Simmer 10 minutes then add the spinach or other greens and cook until greens are wilted. With spinach or other tender greens, this will only take a minute or two. For kale, collards or other more sturdy greens, it will take a bit longer. Stir in the balsamic vinegar. Taste for seasoning and adjust as necessary. Serve with some grated Pecorino Romano (just a suggestion).