Sausage, White Bean, and Spinach Soup

This was really good.  We had it for dinner last night, I had it for lunch today, and I'm actually kind of looking forward to having it for lunch again tomorrow.  And I don't normally care for leftovers or soup.  

Sausage, White Bean, and Spinach Soup
12 oz andouille sausage or chorizo (I used chicken andouille sausage), diced
1 small onion, very fine dice
2-3 tbsp olive oil
2 tbsp tomato paste
5 cups chicken or vegetable stock
14 oz can diced tomatoes, undrained
1 small can cannelini beans, drained and rinsed
2 tbsp corn starch dissolved in about 2 tbsp water (optional)
6 oz bag baby spinach
grated Parmesan cheese for serving (optional)

In a large pot, saute the onions over medium heat for about 5 minutes, until they are beginning to soften.  Then add the diced sausage, up the heat to medium-high and cook for about 5-10 more minutes.  (You want the onion to be really soft and translucent, not browned.  If it's starting to brown, lower the heat).

Add the tomato paste to the sausage and onion mix, and stir to coat.  Then add the stock, diced tomatoes and beans.  If you like your soup with a slightly thicker base, add the cornstarch.  If you don't mind thinner soup, omit it.  Simmer, uncovered, for about ten minutes.

Add the spinach a few handfuls at a time, stirring until it's wilted.  Serve topped with Parmesan, if desired.  (We had grilled Iberico cheese sandwiches alongside.  So good!)