Open and drain the can of water chestnuts, and rinse them. Chop them into small pieces using a knife, vegetable chopper, or food processor.
Wash the portobello mushrooms thoroughly, removing any dirt. Cut them into fours and chop them into small pieces using a knife, vegetable chopper, or food processor.
Press 1 1/2 blocks of extra firm tofu to remove excess moisture. Cut these into small cubes using a knife or a vegetable chopper.
To prepare the rice vermicelli noodles for frying, break them up a bit. They usually come in packets as very long noodles, but these will be much harder to fry, so I recommend breaking them up a bit before frying.
In a deep frying pot, pour some neutral oil (e.g. vegetable oil) and bring to a high heat. Drop a few noodles in the pot to test if the oil is hot enough. If the oil is hot enough, the rice noodles will puff up immediately (after 1-2 seconds). If not, wait a little longer. Once the oil is hot enough, fry your rice noodles by dropping a handful in at a time, and letting them puff up for 1-2 seconds. Flip them over and fry for another 1-2 seconds. After this, immediately remove them from the pot. For this step, you have to be very quick, as the noodles will burn easily if you leave them for even a second too long.
In a medium-sized pan, pour some toasted sesame oil and pan-fry your tofu cubes until golden brown, flipping them around frequently to ensure even frying.
In another pan, sauté the garlic and ginger and sauté until fragrant, for about a minute or two. Add in the shallots and sauté for another minute or two.
Add in the chopped water chestnuts and mushrooms and sauté for a couple of minutes, until the water chestnuts and mushrooms are well cooked.
Add in the fried tofu cubes and mix.
Add in the cilantro and green onions and mix.
Add in the sauces and seasonings. Add the Thai Sweet Chili Sauce, Sriracha, soy sauce, and vegetarian oyster sauce. Add garlic powder, onion powder, and MSG to taste. Cook for a few more minutes so that the veggies and tofu absorb the sauce.
Assemble your tofu lettuce wraps by placing some tofu in each of the lettuce cups. Top with the fried rice noodles and enjoy as an appetizer or snack!