Preheat the Blackstone to medium heat and the air fryers to high.
Add 1–2 tsp oil to the griddle. Sauté the onions and mushrooms until the onions soften and the mushrooms are tender. Stir in the collards, plant-based protein, garlic, seasoning, and Worcestershire sauce. Cook for 2–3 minutes, then add the cream of celery and water. Mix until combined, then turn off ¾ of the burners.
Fill an oven-safe dish halfway with the cooked mixture. Spread the leftover mashed potatoes on top and score with a fork. Brush with egg wash and place in the air fryer for 10–12 minutes.
While the pies cook, place a small pot on the hot side of the griddle. Melt the butter, then whisk in the flour. Season with Essential Blend and thyme, then whisk in the vegetable stock. Continue whisking until the gravy thickens.
Remove the cottage pies from the air fryer and spoon the gravy over the top.
