Created by Derf on May 31, 2013
Step 1: Preheat oven to 350f degrees.
Step 2: Peel and slice the potatoes very thinly (a mandolin works best to get them very thin).
Step 3: Peel and slice the onions medium-fine (again the madolin, if you have one).
Step 4: Melt the butter and pork fat, (you can replace the pork fat with butter, but the taste will be different), in a large iron frying pan over a medium low heat and add the onions, cooking them for 4 to 5 minutes until transparent before adding the potatoes.
Step 5: Season well with salt and pepper.
Step 6: Turn them over occasionally with a wooden spatula and when they have coloured to the blond stage, mix in the parsley.
Step 7: Empty the contents of the pan into a large oval gratin dish and cook very slowly in the oven for at least 1 hour or until browned and crusted on the surface and melting underneath.