Bring water to a boil in a pot. Add a teaspoon of salt and a few drops of oil. Put in macaroni and boil for eight to nine minutes or until al dente. Drain.
Heat oil and saute garlic till golden and fragrant. Add button mushrooms, sausage and macaroni. Mix well. Dish out into a mixing bowl. Stir in mixed vegetables.
Grease a deep square casserole dish lightly with corn oil and pour half of the cooked macaroni mixture into it. Sprinkle with grated cheese and top with the remainder of the mixture. Sprinkle with cheese sparingly all over.
Pour the egg mixture over the macaroni and bake in a preheated oven at 180 ºC for 30 to 35 minutes or until egg mixture sets. Remove and serve either hot or cold.