Place pork and beef in a bowl; rub heavily with salt; let sit at room temperature for 1 hour. Rinse meat, dry with paper towels, and cut into ¼″ cubes. Heat oil in an 8-qt. saucepan over medium-high heat. Working in batches, add pork and beef; cook until browned, about 10 minutes.
Add garlic, onion, and habanero; cook until soft, about 10 minutes. Add taro and scallions; cook until beginning to soften, about 5 minutes. Add stock, allspice, pepper, thyme, and bay leaves; boil. Reduce heat to medium; cook until meat and taro are tender, about 30 minutes. Add collard greens; cook until wilted, about 10 minutes. Season with salt and pepper.
