Ribollita (Tuscan-style Bread Soup)

Preheat the oven to 425°F with a rack placed in the center of the oven. Tear the bread into 2-inch chunks and spread on a baking sheet. Transfer to the oven and toast the bread for about 5-7 minutes, until a light crust forms on the chunks of bread.
While the bread toasts, heat the olive oil over medium-low heat in a large pot. Add the onion and garlic and let it cook, stirring occasionally, until the onions are translucent, about 5 minutes.
Stir in the celery, carrots, and squash, and cook for another 3-5 minutes.
Add the broth, crushed tomatoes, beans, oregano, and bay leaf, and bring to a boil. Lower the heat to a simmer, and let it continue cooking until the carrots and celery are tender. Stir in the bread; this will make the soup thicker and creamier.
Drop in the greens and adjust the seasoning with salt and pepper. Add parsley.
Serve immediately with a drizzle of olive oil, grated Parmigiano Reggiano, and red pepper flakes sprinkled on top. Enjoy!