Sauté the Base: Heat the olive oil in a large pot or Dutch oven over medium heat. Add the onion, carrots, and celery. Sauté for about 5–7 minutes until the vegetables begin to soften.
Add Aromatics: Stir in the minced garlic and red pepper flakes (if using). Cook for just 1 minute until fragrant.
Simmer the Broth: Add the cubed potatoes, canned tomatoes (with their juices), and the broth. Season with oregano, salt, and pepper. Bring the mixture to a boil, then reduce heat to low and simmer for 10 minutes.
Wilt the Cabbage: Stir in the chopped cabbage. It might look like a lot at first, but it will wilt down significantly. Cover the pot and simmer for another 20–25 minutes, or until the potatoes are fork-tender and the cabbage is silky and soft.
The Finishing Touch: Taste and adjust the seasoning. If the soup is too thick, add a splash more broth.
Serve: Ladle into deep bowls. Top with fresh parsley, a drizzle of high-quality olive oil, and plenty of grated cheese.
Tips for the Best Bowl
The Bread Factor: This soup practically begs for a thick slice of toasted sourdough or crusty Italian bread rubbed with a raw garlic clove.
The “Nonna” Secret: If you have an old Parmesan cheese rind in your fridge, drop it into the pot while the soup simmers. It adds a deep, savory umami flavor that salt alone can’t replicate.