Place the cashews in a bowl, cover with water and allow to soak for several hours or over night. (Alternatively, you can cover with water, heat to a simmer and turn off the heat and allow to soak for at least an hour)
Drain and rinse the soaked cashews.
Place cashews in a food processor or high speed blender with the lemon juice, salt and about half the liquid. Pulse to process scraping the sides down as necessary. Add the remaining liquid and process for several minutes until extremely smooth.
Preheat oven to 350º F
Combine the salsa verde and cashew sour cream in a medium sauce pan and heat slowly until warm. Season will salt and pepper to taste.
Mix approximately 1 1/2 cups of the salsa/sour cream mixture with the shredded chicken.
Roll 1/8th of the chicken mixture in each of the tortillas (about 1/3-1/2 cup each) and assemble the chicken enchiladas, side by side, in a pan (use 9 x 13 or similar size/shape).
Top the chicken enchiladas with the remaining salsa/sour cream mixture. (Thin out the sauce with extra chicken stock if it is too thick after heating)
Cover with aluminum foil and heat in the oven for 30 minutes or until heated through.
Remove from the oven and top with slices of avocado and scallions. Serve immediately.