Boil macaroni in sufficient water till soft. Drain water and keep it under running water then strain and keep aside.
Take a pan and melt 1 tsp of butter and add purpose flour and saute for 1 minute. Add milk and mix continuously so that no lumps will be formed.
Add grated cheese and 1/2 tsp black pepper powder and mix well. White sauce is ready. Keep aside.
Heat remaining butter in an another pan. Add onion, carrots and beans. Saute for 1-2 minute. Add salt and pepper powder. Mix well. Add White sauce and stir continuously.
Lastly add boiled macaroni and so that macaroni will coat well with the sauce.
Serve hot sprinkle with oregano.
