In a large bowl, combine the syrup, mustard, chili paste, vinegar and molasses. Separate the ribs and toss with the mixture; cover and refrigerate for 2 hours or overnight.
Preheat the oven to 375 degrees. Place the ribs on a foil-lined baking sheet and season with salt and pepper. Place the marinade in a saucepan, bring to a boil, then remove from the heat. Roast the ribs, basting with marinade every 10 minutes and flipping after half an hour, until tender, about 50 minutes. Sprinkle with the sesame seeds.
