Heat a large, heavy bottomed pan over medium-high heat. Heat vegetable oil and add diced onion. Saute until onions are beginning to softed; 3-4 minutes
Crumble Italian Sausage and garlic with the onion. Cook until sausage is no longer pink; about 4-5 minutes. Drain any excess grease.
Stir in crushed tomatoes, vegetable (or chicken) broth, basil, salt and pepper. Bring to a boil, cover and reduce heat to low. Simmer for about 20 minutes.
Add tortellini and spinach and simmer for about 5-10 minutes, or until pasta is tender.
Garnish with shredded Parmesan and serve with a cheesy crostini crouton.
Slice baguette into 1/2 inch thick slices. Butter one side and place butter side down in a hot skillet until golden brown. Flip bread slices over and sprinkle with Parmesan while the other side gets golden brown. Transfer to a plate and immediately cover loosely with foil if cheese has not completely melted.
For a creamier soup, add a half cup of Greek yogurt or sour cream.