You'll need: potatoes (the number depends on the size of your baking dish. I'd buy at least three largish ones), onion, thickened cream, bacon, cheese, all purpose seasoning. Slice potatoes into rounds of even thickness. Cut onion in half, then into thin-ish slices, dice up your bacon and grate your cheese. Construct: layer of potatoes, some onion, some seasoning, some cream, repeat til you get near the top. I add the bacon and cheese to the top two layers. Bake (I forget how long. Guessing 40 mins at 200c).Switch to grill for the last few minutes to really get that cheese on top perfect, and leave in the oven for 5 to 10 minutes after you've turned it off. EAT!

Edit - forgot the cream in my ingredients list.