Soak the walnuts for 6-8 hours, rinse well and drain. Dry them in the dehydrator on 115℉ (46℃) for about 18 hours until completely dry.
If you don't own a dehydrator (it will no longer be raw):
Lightly toast the walnuts on a dry skillet until they start to smell fragrant. Set aside and cool off.
Soak the sun-dried tomatoes in water to soften. Drain and roughly chop.
Add all the ingredients for the walnut taco meat into the food processor, and pulse until the walnuts become the size of ground taco meat. Do not process too much. It should look like crumbles. If you process it too much, it will become a taco meat paste!
Pico de gallo
Dice the tomatoes and onion. Mince the garlic and jalapeno. Roughly chop the cilantro.
Add salt and lime juice and toss together.
Assembly
Rinse and dry off the lettuce leaves, and cut the ends off to fit the plate if needed.
Line it up on the plate and place about 1½ - 2 Tablespoons of the walnut taco meat onto each leaf. Top with some pico de gallo. You can also add some guacamole or sliced avocados.