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 half of the green onions, water chestnuts, soy, hoisin, and rice vinegar. 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.
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!