This recipe makes a lot - two 9x13 in. pans, so you might want to halve it:
10 lbs potatoes, peeled
2 onions, peeled
1 1/2 tbl. salt
1/4 cup oil (I'd use canola or something equally neutral)
Preheat oven to 450 deg. Grate the potatoes and onions (I use the juicer, and then just return most of the liquid to the pulp - much faster than grating by hand and better texture than food processor). Stir together with remaining ingredients.
Grease your baking pans very well. Divide the mixture between the pans.
Bake for 20 minutes at 450 and then reduce the temperature to 400 deg. Cook until done, about an hour longer - it should be golden brown.