1/2 cup cane or rice vinegar, plus more for serving
2 T. soy sauce
2 T. freshly minced garlic (about 6 medium cloves)
1 1/2 tsp. freshly ground black pepper
1 tsp. oyster sauce
1 tsp. yellow mustard
1 tsp. kosher salt, plus more for seasoning
1 rack St. Louis-cut pork spareribs, cut into 1-inch strips across the bone, then cut between each bone into individual portions
6 T. cornstarch
Canola or peanut oil, for deep frying

In a small bowl, whisk together vinegar, soy sauce, garlic, pepper, oyster sauce, mustard, and 1 tsp. salt. Place rib pieces in a large zipper-lock bag. Pour in marinade, seal tightly, and toss to distribute marinade evenly. Place in refrigerator and marinate for at least 4 hour or up to overnight, turning bag at least once during that time. Fill a wok or Dutch oven at least 4 inches deep with oil and heat to 375°F over high heat. Working in batches, transfer 1/3 of ribs to a medium bowl (they should be wet and dripping with marinade), add 2 T. cornstarch, and toss until ribs are evenly coated in a sticky, paste-like batter. Carefully lower ribs, one at a time, into hot oil and fry until golden brown, about 7 minutes, stirring occasionally for even cooking. Transfer to a paper towel-lined plate and season lightly with salt. Repeat with remaining ribs. Serve immediately with vinegar for dipping.