Add oil to a pot of boiling salted water. Add the macaroni and cook according to the directions in the package. (This took the longest time for me - around 15-20 minutes. Keep checking every couple of minutes past the 10 minute mark. You don't want your macaroni mushed from over cooking.)
In a wok, melt butter and add the flour and over medium heat, stir it for 5 minutes. Add milk and cook it for 2-3 minutes until the sauce has thickened. Turn off the gas. Add cheese,salt and pepper and mix well.