Heat olive oil in a large pot over medium heat. Add onions, carrots, and celery. Sauté for 5–7 minutes until vegetables begin to soften.
Stir in the mushrooms and cook for another 5 minutes until they release their moisture and become golden.
Add garlic and cook for 1–2 minutes, stirring constantly.
Pour in the chopped tomatoes and drained white beans. Add enough water to cover all ingredients.
Season with salt and black pepper or a few whole peppercorns. Stir well.
Bring to a boil, then reduce the heat and let simmer for 20–30 minutes until all the vegetables are tender and the flavors are well combined.
Taste and adjust seasoning if needed. Serve warm.