For sauce, in a screw-top jar combine milk and flour. Cover and shake well. Pour into a saucepan; cook and stir over medium heat until bubbly. Add cream cheese; cook and stir until melted. Remove from heat; stir in chives.
Lightly coat a large skillet with cooking spray. Heat skillet over medium-high heat. Add mushrooms and onion. Cook and stir about 3 minutes or until vegetables are tender. Add the mushroom mixture to sauce. Stir in chicken; set aside.
In the same skillet melt butter over medium heat. Add egg product, salt, and pepper. Cook over medium heat, without stirring, until egg mixture begins to set on the bottom and around edge. Using a spatula or a large spoon, lift and fold the partially cooked egg mixture so that the uncooked portion flows underneath. Continue cooking over medium heat until egg mixture is cooked through but is still glossy and moist. Transfer egg mixture to a 2-quart casserole; spoon the sauce over top.
Bake in a 400 degree F oven about 15 minutes or until heated through. Let stand for 10 minutes before serving. Makes 6 servings.