Boil water, salt and cooking oil. Cook the macaroni, drain and keep aside. In a pan, heat 1½ tablespoons of butter and add the vegetables. Sauté well, add salt and 1 teaspoon of pepper. Keep this aside. In another pan, heat the rest of the butter and add maida. Mix well till the raw smell goes off and add the milk. Whisk well. Add salt and the rest of the pepper. Mix in the cooked macaroni and vegetables. Season with oregano and add the black olives.