Toast the walnuts in a dry skillet over medium-low heat for 4 to 5 minutes, stirring frequently, until they smell toasty and are darker in spots.
Alternatively, spread walnuts on a sheet pan and toast in a preheated oven at 350ºF/175ºC for 7 minutes.
Add the toasted walnuts to a food processor and pulse until very finely chopped, being careful not to over-process.
Add the chopped mushrooms, salt, black pepper, Homemade Taco Seasoning, lime juice, and soy sauce to the food processor. Blend until very finely chopped but not smooth.
Heat a large nonstick frying pan over medium to medium-high heat with avocado oil.
Add the walnut-mushroom meat and cook for 2 minutes, breaking it up into small pieces.
Cook for another 3 to 5 minutes, or until browned and slightly crispy.
To reheat, add taco meat to a frying pan over medium heat until warmed through and slightly crisp.