Start by preparing your workspace. Gather all the ingredients and a large mixing bowl. If you're using a rack of baby back ribs, remove the membrane from the back. This helps tenderize the meat and allows the rub's flavors to infuse better.

In your mixing bowl, combine the dark brown sugar, Chinese five-spice powder, fine sea salt, garlic powder, smoked paprika, and black pepper. Mix until it’s well-combined. You should have a delightful blend that smells amazing!

Next, grab your ribs and add a layer of yellow mustard onto the meat. This step is crucial. Not only does the mustard help the rub stick, but it also adds a tangy base flavor. Sprinkle the dry rub generously over the ribs, ensuring every surface is covered. Massage it into the meat for better flavor penetration.

After rubbing the spices in, let the ribs rest for at least 30 minutes. If you can let them sit for a few hours or overnight in the refrigerator, that would deepen the flavor even more.

Preheat your grill or oven. If you're using a grill, set it to indirect heat, around 300°F (150°C). If baking, place the ribs on a baking sheet covered with aluminum foil. Cook them low and slow for about 2.5 to 3 hours.

While the ribs are cooking, combine the dark soy sauce, oyster sauce, mirin, rice vinegar, and cornstarch in a saucepan over medium heat. Stir constantly until it thickens, creating a silky sauce that pairs wonderfully with the ribs.

To finish the ribs, you can brush them with the Au Jus during the last 30 minutes of cooking. This adds extra flavor and moisture. You might also want to glaze them on a barbecue for a few minutes before serving to catch that charred essence.

Once cooked, allow the ribs to rest for 5-10 minutes. Then, slice between the bones and serve with more Au Jus and your favorite sides. Watch your guests’ faces light up—worth every minute spent in the kitchen!