Drain the beans and combine with 1 qut fresh water in Dutch oven or large pot. Bring to a simmer. Skim off any foam, add the bouquet garni. Reduce heat, cover and simmer 1 hr. Add 1 tsp salt.
Meanwhile rinse the chard leaves and stem. Dice the stems, cut the leaves in ribbons or coarsely chop, and set aside.
Heat the olive oil in a heavy nonstick skillet and add the onion and chard stems. Cook, stirring often until tender, about 5 min. Add the garlic and continue to cook, stirring until the garlic is fragrant, about 1 min. Add the potatoes and stir together, transfer to the pot with the beans. Bring back to a simmer, cover and simmer 30 min., until the potatoes and beans are tender.
Add the chard and thyme leaves to the pot, cover and simmer for 15 min. Stir in freshly ground pepper to taste and the parsley. Taste, adjust the seasoning and serve with freshly grated Parmesan on top of serving.
Can be prepared ahead up until the addition of the chard shortly before serving to maintain color.