Start by making the corn salsa: in a medium bowl, combine the corn kernels, lime juice, salt + pepper and red onion. Toss to combine. Let this sit for a while (about 15 minutes, stirring here and there). Add the tomatoes and coriander and stir to combine. Check the mixture for seasoning and set aside.
Make the spicy walnut meat: throw all of the ingredients in a food processor and pulse the mixture until a chunky paste forms. Season it to your liking, move it into a bowl and set aside.
Make the cashew sour cream: drain the cashews and place them in a blender. Add all of the other ingredients and blend on high until a smooth paste is achieved. You may have to scrape down the sides a couple times and add some extra water. Once the mixture is smooth and tasting creamy + sour, store it in a bowl in the fridge.
To serve: lay lettuce leaves on a platter.Divide the walnut meat among the shells. Then, scoop some corn salsa into each shell as well. Garnish each taco with some sliced avocado, cashew sour cream, a little chili and some chopped coriander.