Step 1: Heat the olive oil in a large, heavy-bottomed pot or Dutch oven over medium heat. Add the diced onion, carrots, and celery. Sauté for 8-10 minutes, or until the vegetables have softened and become translucent, stirring occasionally.
Step 2: Add the minced garlic and dried oregano to the pot. Cook for another 1-2 minutes, stirring constantly, until fragrant. Be careful not to let the garlic burn.
Step 3: Pour in the crushed tomatoes, vegetable broth, and add the bay leaf. Stir everything well to combine. Bring the mixture to a gentle simmer, then reduce the heat to low, cover the pot, and let it cook for at least 20-30 minutes to allow the flavors to meld.
Step 4: While the soup is simmering, rinse and thoroughly drain the cannellini beans. For a creamier, thicker soup, you can mash about a quarter of the beans with a fork before adding them to the pot.
Step 5: After the simmering time, add the rinsed cannellini beans and the ditalini pasta to the pot. Increase the heat to medium-high and bring the soup back to a boil. Cook, stirring occasionally to prevent the pasta from sticking, until the ditalini is al dente (tender but still firm to the bite), typically 7-10 minutes or according to package instructions.
Step 6: Remove and discard the bay leaf. Season the pasta fagioli generously with salt and freshly ground black pepper to taste. If the soup appears too thick for your preference, you can stir in a little more vegetable broth or water until it reaches your desired consistency.
Step 7: Ladle the hot pasta fagioli into individual serving bowls. Garnish each bowl with a generous sprinkle of freshly grated Parmesan cheese, a drizzle of high-quality extra virgin olive oil, and a scattering of fresh chopped parsley. Serve immediately with crusty bread and enjoy!