Step 1

Place racks in upper third and middle of oven; preheat to 350°. Line a rimmed baking sheet with a double layer of foil. Mix 3 Tbsp. brown sugar, 1 Tbsp. kosher salt, and 1 Tbsp. Chinese five-spice powder in a small bowl to make a rub.

Step 2

Cut 2 3-lb. racks St. Louis-style ribs in half (to create 4 smaller pieces). Transfer to prepared sheet. Season all over with spice rub, being sure to coat sides and edges and to gently press the rub into the meat. Pour 1½ cups water into baking sheet, then cover tightly with foil. Bake on middle rack until meat is very tender and bones are exposed, 100–115 minutes. If racks of ribs you're cooking are much smaller than called for, check early—they'll cook in less time.

Step 3

Meanwhile, whisk ½ cup hoisin sauce, ½ cup soy sauce, 3 Tbsp. honey, and remaining 1 tsp. Chinese five-spice powder in a small saucepan to combine.

Step 4

Peel and finely grate 4" piece ginger and 5 garlic cloves into saucepan. Heat over medium and bring to simmer, whisking often. Cook, stirring, until just thick enough to coat the back of a spoon, 2–3 minutes longer. Cover pot; set aside until ribs are ready.

Step 5

When ribs are cooked and tender, carefully remove and discard top layer of foil from baking sheet. Preheat broiler.

Step 6

Brush half of sauce over ribs, turning ribs with tongs to coat both sides. Arrange flesh side (convex side) up. Transfer to top rack of oven and broil until ribs are lacquered in sauce and caramelized in some parts, 4–5 minutes. Remove from oven and brush remaining sauce over.

Step 7

Transfer ribs to a cutting board. Cut in between each bone to separate ribs. Transfer to a platter or serve right off cutting board.