Optional Crispy Rice Noodles: To make crispy rice noodles as shown in photos, heat about ½ inch of oil in a large saute pan over medium high heat. Drop a single rice noodle into the oil. When it bubbles, the oil is hot enough. Working in batches, drop the noodles into the hot oil cooking for just a few seconds until they puff up. Remove from oil and set on a paper towel.
Tofu: Drain tofu and wrap in a few layers of paper towels. Squeeze to remove excess moisture, then use your hands to crumble up the tofu. Heat oil in a large saute pan or wok over medium/high, then add the tofu. Cook until it begins to turn golden at the edges, 7 to 10 minutes.
Veggies: Add the onion, mushrooms, garlic, and ginger. Cook until mushrooms have released their moisture and it evaporates. Onion should be soft at that point, about 10 minutes.
Flavor: Add water chestnuts, soy, hoisin, rice vinegar, and half of the green onions. Cover and cook for 2 to 3 more minutes.
Serve: Spoon filling into each butterhead lettuce leaf, topping with remaining green onions and optional crispy rice noodles.
Notes
Serve with your favorite dipping sauce, such as sriracha mayo (4 Tbsp mayo, 1 Tbsp sriracha, squeeze of lime) or the almond butter dipping sauce in this recipe!