This recipe is basically a mashed potato pie with melted cheese on top, nothing wrong with that! Seasoned mashed potatoes are mixed with cheese and spread into a pie pan. Then more cheese is added on top and the potato pie is baked in the oven.
You don’t have to use 2 onions; I only use 1 or half if using a large onion. I didn’t want onion pie, I wanted potato pie. Using too onion much overpowers the potatoes. Substitutions can be made for whatever cheese you want or whatever type of potatoes you want, just match the weight with the russet potatoes called for in the recipe. Spray the baking pan; it will make your life easier. This is can be made ahead, assemble but don’t bake. Cover and refrigerate until ready to bake. If you let this sit 5 to 10 minutes after baking, it will slice cleaner into neat wedges; otherwise you get a mashed potato pile with melted cheese on top. Don’t get me wrong, it still tastes great, it’s just not as pretty.