Preheat oven to 400. Coat 7x11 in pan with cooking spray.
In small bowl mix cornstarch with water and set aside.
In a large non-stick skillet, heat sesame oil over high. Add scallions, ginger and garlic and cook, stirring constantly until fragrant, about 2 minutes.
Add Chicken, mushrooms and carrots. Cook until vegetables begin to soften, about 4 minutes. Add coleslaw mix and vinegar and cook, stirring constantly until cabbage begins to wilt and becomes translucent, about 4 minutes. Push mixture to edge of skillet.
Stir corn starch mixture to recombine and pour into the centre of the skillet. Stir into the vegetables thoroughly, then cook for about 1 minute. Transfer mixture to a bowl and stir in 1/2 cup hoisin sauce.
Place 2 eggroll wrappers over the bottom of the prepared baking dish. Spread with 1/3 of the vegetable mixture. Cover with 2 more egroll wrappers then spread with 1/2 the remaining filling.
Repeat with 2 more wrappers and the remaining filling. Top with the 2 remaining wrappers.
Spray a piece of foil with non-stick cooking spray and tightly cover dish. Bake for 20 minutes. Uncover and brush with remaining Tbsp hoisin sauce. Sprinkle with sesame seeds. Replace foil and bake 10 mins more until casserole bubbles at the edges and is heated through to the centre.
Serve, or let cool completely before covering tightly with foil and plastic wrap, then refrigerate or freeze.