In a large pot over medium heat, add the olive oil and the butter. Once it's hot and the butter has melted, stir in the onions, celery and carrot with a big pinch of salt. Cook, stirring occasionally until they have begun to soften up, about 3-5 minutes. Then stir in the tomato paste, garlic, oregano, thyme and basil. Cook about 2-3 minutes more, stirring pretty often.
Pour a bit of the broth in and deglaze the pan. Then the rest with the crushed tomatoes and bay leaves. Increase the heat to med-high and let this come up to a simmer. Once its simmering, stir in the beans, potatoes, zucchini and yellow squash along with the salt and pepper. Let this all simmer together until the veggies are all tender. Last, take out the bay leaves and stir in the chopped spinach and let it wilt down. Taste and add more salt, pepper, etc until you're happy with the flavor.
While the soup is coming to a simmer, heat a separate pot of salted water over high heat. Once its boiling, cook the ditalini pasta according to package directions, then drain and set it aside until the soup is done.
To serve, you can stir the cooked pasta into the soup, or if you're going to have a lot of leftovers, you can just keep them separate and add the pasta to individual bowls and pour the soup over top of it... that way the pasta won't absorb all the liquid.
