Caramelized Tofu Lettuce Cups

Name: Caramelized Tofu Lettuce Cups
Ingredients: 1 (14-oz.) block firm tofu, drained; 1/4 c. reduced-sodium soy sauce; 3 tbsp. packed dark brown sugar; 2 tbsp. unseasoned rice vinegar; 1 tsp. toasted sesame oil; 1/2 tsp. red pepper flakes; 1/2 tsp. fish sauce (optional); 2 tbsp. vegetable oil; 1 fresh ginger, minced; 2 cloves garlic, minced; Butterhead or romaine lettuce, leaves separated, for serving; Cilantro leaves, for serving; Chopped roasted peanuts, for serving; Lime wedges, for serving