Boil the macaroni in water with a bit of salt and 1 tablespoon of soybean oil. Strain the boiled macaroni and set aside.
Heat a pan with 2 tablespoons of soybean oil and add the onion slices. Fry until the onions turn slightly red in color. Add the ginger and garlic pastes, black pepper powder and minced beef. Stir and mix well.
When the water released from the beef dries up and the oil starts to float on top, add the tomato ketchup.
Mix well to form a thick gravy.
Now to prepare the white sauce, heat a pan with butter. Add the flour and stir. Do not allow the color of the flour to change as you fry it-so stir continuously.
Add salt and black pepper powder.
Stir continuously as the milk is poured. Cook until a thick sauce forms. Set this white sauce aside.
Mix the strained macaroni with the cooked minced beef. Set aside.
Grease a serving dish with a bit of oil. Make layer of the macaroni and beef mixture. Spread the white sauce all over and repeat to make another layer of macaroni and beef.
Sprinkle all of the grated cheese to make the top layer.
Preheat a baking oven at 180 degree Celsius for 10 minutes.
Bake the mosaka for 15-20 minutes at 175 degree Celsius. The baking should be complete when the top layer turns brown and the flavorful smell of mosaka comes out.