1. Heat the oil in a large stockpot over medium-low heat. Add ham, and cook until it starts to release juices, about 2 minutes; do not brown. Add onions and garlic; cook, stirring occasionally, until soft, about 10 minutes.

2. Working in batches, if necessary, so as not to overcrowd pot, cook collard greens, tossing frequently with tongs until thoroughly wilted. Add tomatoes and juice, chicken and beef stocks, potatoes, thyme, and parsley. Bring to a boil, and reduce heat to a gentle simmer; cook, stirring and skimming any foam from surface occasionally, until potatoes are easily pierced with a paring knife, 30 to 40 minutes. Remove from heat; season with salt, black pepper, and hot-pepper sauce, as desired. Serve hot.