How to Make It
Combine sugar and salt in a small bowl. Place pork in a large bowl; rub evenly with sugar mixture. Cover and refrigerate overnight.
Preheat oven to 300°. Place pork on a rack set inside a roasting pan. Place pan in oven; bake 4 hours or until a thermometer registers 210°, basting occasionally with drippings. Remove from oven; let stand 30 minutes. Shred pork with 2 forks.
Combine ginger and next 5 ingredients (through soy sauce), stirring with a whisk. Stir in onions. Reserve half of sauce. Toss shredded pork in remaining half of sauce. Divide pork evenly among lettuce leaves. Top with radishes; drizzle with reserved sauce. Serve with lime wedges, if desired.