Heat oven to 200ºC Grease 25 cm pie plate. Mix chicken, corn and Taco mix; spread in plate. Sprinkle with chilies and cheese. Beat remaining ingredients until smooth, 15 seconds in blender on high or 1 minute with hand beater. Pour into plate. Bake until knife inserted halfway between center and edge comes out clean, 25 to 30 minutes. Cool 5 minutes. Serve with sour cream and lettuce.