Bring a large pot of water to a boil. Add the ribs, garlic and ginger. Bring back to a boil and let simmer until tender, 25 to 30 minutes. Turn off the heat and let the ribs sit for about 5 minutes.
Meanwhile, preheat the oven to 400 degrees F. Line a large rimmed baking sheet with aluminum foil.
In a saucepan, combine the hoisin sauce, soy sauce, sugar, vinegar and five-spice powder. Heat over medium heat, stirring occasionally, until the sauce is smooth and thick, 7 to 10 minutes.
Drain and pat dry the ribs with paper towels. Place the ribs on the prepared baking sheet and brush all over with the sauce.
Roast for 30 minutes, basting with more sauce every 15 minutes.
Cut the ribs into 2-rib portions and place in airtight containers. To serve, place the ribs on a metal tray and brush with the remaining sauce. Toast with a propane kitchen torch to caramelize further. Sprinkle with sesame seeds and serve hot or at room temperature.
Propane gas torches are highly flammable and should be kept away from heat, open flame and prolonged exposure to sunlight. They should be used only in well-ventilated areas. Follow torch manufacturer's instructions for use.