Make the Marinade
In a bowl, whisk together brown sugar, garlic, soy sauce, vinegar, Dijon mustard, olive oil, paprika, salt, and pepper. Add red pepper flakes if using.
Marinate the Ribs
Place the lamb ribs in a large zip-top bag or dish. Pour the marinade over the ribs, ensuring they are fully coated. Cover and marinate in the fridge for at least 2 hours, preferably overnight.
Preheat Oven and Prep Pan
Preheat oven to 325°F (160°C). Line a baking sheet with foil and place a wire rack on top. Arrange the ribs on the rack, reserving excess marinade.
Bake the Ribs
Bake for 1 hour, basting with reserved marinade halfway through. Increase oven to 400°F (200°C) for the last 10–15 minutes to caramelize the glaze.
Rest and Serve
Let the ribs rest for 5–10 minutes after baking. Garnish with chopped parsley and serve hot.