The oyster mushrooms should be separated into individual large pieces, but group the smaller mushrooms into groups of 2 or 3 connected by the stem.
Prepare your dredging stations. To make the liquid batter, combine nondairy milk with apple cider vinegar, hot sauce and flax meal in a large bowl. Mix the cornstarch with a small amount of the vegan milk mixture to make a slurry and then add it back into the bowl. Add the mushrooms and let them soak for at least 15 minutes. In the meantime, continue on with the rest of the recipe.
In another large bowl, combine the flour with the sea salt, chili powder, garlic powder, onion powder, ground white pepper, ground sage, coriander, smoked paprika, celery salt, ground nutmeg, ground cinnamon, ground cumin and ground allspice.
To make the avocado ranch, in a small food processor add vegan mayonnaise, dill, parsley, chives, apple cider vinegar, onion powder, sea salt, ground black pepper, unsweetened nondairy milk and the avocado. Blend until very smooth.
In a medium to large heavy bottomed pot, heat up frying oil to between 325°F to 350°F.
Once the oil reaches 350°F, start battering the mushrooms in batches. Remove the mushrooms from the liquid and place them on a separate tray. Work with the first batch of mushrooms and place them in the dry batter to coat evenly. Now place the mushrooms back into the liquid batter and then back into the dry batter to double dredge.
Carefully place only 2 or 3 battered mushrooms into the hot oil at a time, using a splatter guard if desired. Fry for 3 to 4 minutes, flipping halfway. Remove from the hot oil with tongs and place on a paper towel to absorb any excess oil.
Grill flour tortillas in a cast iron grill pan over medium heat for 1 to 2 minutes until grill marks appear, but flour tortillas should still be pliable. Alternatively you can broil the tortillas in the oven on a sheet pan on the top rack for about 1 minute, just until the char marks appear, but the tortillas are still pliable.
To make the buffalo sauce, in medium bowl, add melted vegan butter and buffalo-style hot sauce. Brush the hot sauce mixture on both sides of the mushrooms just before serving.
To assemble add napa cabbage to the tortilla, top with the fried oyster mushrooms, red onion, pickle slices and drizzle with avocado ranch. Serve immediately.