Cook the noodles in salted water until they are done and then drain and set aside.
Next, add the oil and 1 tbsp of the light butter in a large satue pan and then add in the onions, and a pinch of salt and cook for 6 minutes and then add in the flour and cook while stirring another 3 minutes.
Then add in the milk, chicken broth, nutmeg and a pinch of salt and pepper and whisk a few minutes until it starts to thicken. Next add in the sherry, peas, mushrooms and some more salt and pepper and cook another 5-7 minutes.
Next, add in the tuna and cheese and stir until the cheese has melted and then turn off the heat. Then, add the noodles to the sauce mixture and stir to coat evenly.
Last, rub the other 1/2 tbsp of butter to coat the bottom of a casserole dish and pour in the tuna mixture and top with the crushed potato chips.
Bake at 375 for about 25 minutes and cover with foil halfway through so the chips don't burn and serve immediately!
I created this the other night and it is so good! :)