Heat oven to 200ºC Grease 25 cm pie plate. Brown hamburger with onions, then drain grease. Stir in garlic, chili powder, oregano, salt, pepper and half C of Enchilada sauce. Sprinkle crushed tortilla chips evenly in the pie plate. Top with 1- half C of the cheese; spread with meat mixture. Beat milk, eggs and Bisquick until smooth, 15 seconds in blender on high. Pour into pie plate. Bake until knife comes out clean, 25 to 30 minutes. Spread remaining sauce over top, sprinkle with remaining cheese. Bake until cheese is melted, 3-5 minutes longer. Cool 10 minutes before serving. Can top with sour cream if desired.