Pasta e fagiole

My cooking library harbors many strange and wonderful books. Gentlemen, Start Your Ovens: Killer Recipes for Guys, by Tucker Shaw, falls into both categories. Don't be fooled by the title; the author sets out to demystify cooking for everyone. This slightly-adapted recipe, for a quick version of the classic soup known hereabouts as "pasta fazool", serves 4.

2 Tbsp unsalted butter
2 Tbsp olive oil
1 onion, chopped
1 carrot, peeled and chopped
1 stalk celery, chopped
2 cloves garlic, smashed and finely chopped
Pinch of kosher salt
Fresh ground black pepper, to taste
1 Turkish bay leaf
4 cups chicken stock (homemade or store-bought low-sodium) or vegetable stock
14 oz canned diced tomatoes, with their juice
1 Tbsp ketchup
15 oz canned cannellini beans
1/2 lb dried spaghetti, broken into pieces 3-4 inches long, or any stubby pasta
5 oz bag of baby spinach leaves

In a stock pot over medium-high heat, melt the butter with the olive oil. Add the onion, carrot, celery, garlic, salt and pepper to taste, and sauté until the vegetables are soft. Add the bay leaf, chicken stock, tomatoes and juice, ketchup and cannellini beans. Bring to a boil, then reduce the heat to low and simmer for 15 minutes. Add the pasta and simmer for 10 minutes more, stirring occasionally to keep the beans from sticking. Fish out the bay leaf. Taste and adjust the seasoning. Add the spinach, and stir to combine. As soon as the spinach wilts, the soup is ready. (Note: like many bean soups, this one improves with age. It will be delicious on the first day, and better on the second.)