Slice mushrooms and onion thinly.

Season chicken with salt and pepper, then cut into bite-sized pieces.

Boil water in a pot, cook macaroni for 1 minute less than package instructions, then drain.

Heat salad oil in a pan, cook chicken until color changes, then add mushrooms and onion. Cook until onion is translucent, add macaroni, and stir to coat with oil. Remove from pan.

Wipe the pan clean, melt butter, add flour, and stir over medium-low heat until flour loses its raw smell. Gradually add cold milk, stirring until thickened. Season with salt.

Combine the cooked ingredients with the white sauce, mix well, and transfer to a heatproof dish. Top with pizza cheese and bake in a toaster for 5 minutes until cheese melts.