Heat broiler. Place pineapple on foil lined baking sheet.
In small bowl, combine hoisin, ginger, garlic, and mustard. Place pork on a broiler pan fitted with a rack. Brush with hoisin mixture; season with salt and pepper.
Place pork in broiler about 4 inches from heat. Place pineapple in oven on rack under rack pork is on. Broil pork until is registers 155 degrees, 15 to 20 minute Remove from broiler (let rest at least 10 min before slicing; temp will rise to 160). Turn pineapple slices; cook til browned in spots, about 10 min more.
Halve pineapple slices; arrange on platter with sliced pork. Drizzle with pan juices; season with salt and pepper. Serve with Quick Ginger Sauce.
Quick Ginger Sauce:In small bowl, stir together 2 T each hoisin and pineapple juice, 2 t grated fresh ginger, and 1 t soy sauce. Season with pepper.