In a large 8-quart soup pot, heat oil, onion and garlic together and cook until soft. Add carrots, celery, potatoes, 2 cups of beans, bean cooking liquid (or water) and basic tomato sauce and bring to a boil. Lower heat, add chard, kale, black cabbage and simmer 1 ½ hours until everything is soft. Add remaining beans and adjust seasoning. Allow to cool and rest overnight.
The following day, bring to a boil and serve in shallow bowls over toasted bread.
Sprinkle with parmigiano tableside.
¼ cup extra virgin olive oil plus ½ cup
1 medium red onion, chopped into ½ inch dice
2 cloves garlic, peeled and thinly sliced
1 medium carrot, scraped and chopped into ¼ inch half-moons
2 ribs celery, chopped into ¼ inch thick pieces
2 waxy potatoes, peeled and cut into ½ inch cubes
3 cups white cannellini or brown borlotti beans, soaked and cooked perfectly
6 cups reserved bean liquid (or water)
1 cup basic tomato sauce
1 bunch Swiss chard, chopped into ½ inch ribbons
1 bunch kale, chopped into ½ inch ribbons
1 bunch black cabbage (cavolo nero), chopped into ½ inch ribbons
4 slices country bread, toasted
½ cup grated parmigiano