However, I did these very simple and yummy spuds alongside the meal and they are just so easy you'll kick yourself for not cooking them before.
Heat your oven to about 180C (that's fan temperature. a little higher for standard ovens, though it's not critical). While it's warming up, grease an ovenproof dish. I like using the one in the photo because you can see how things are progressing while it cooks, but that isn't essential. A lid is though. (If you don't have a lidded dish, use foil.)
Peel some potatoes. Any kind, although larger ones look nice when you're done, and cut them into thin slices. Do the same with a couple of onions. If you like garlic, peel and squish a couple of cloves of that too.
Now layer the whole lot into the dish. Start with onions and end with potatoes. Every couple of layers dot the spuds with s bit of butter or a smear of oil. Not too much! And add a sprinkling of salt (JUST a sprinkling - we're not breeding heart attacks here) and a hefty grind of black pepper.
Add enough chicken stock to come about a third of the way up the side of the dish. PLEASE don't use a whole stock cube if you have those nasty, salty commercial ones. A VERY tiny amount will be sufficient.
Now put it in the oven, on the bottom shelf will do, and ignore it for about 40 - 45 minutes. (The first time you cook it you might like to check after half an hour, just in case it's drying out.) If it looks a bit dry, add a small amount of water. (This is where the glass sides come in handy.) After 45 minutes it ought to be browning on top. You CAN leave it for up to an hour and a half, depending on how crunchy you like the top layer, but I find an hour is about right.
It goes with practically any roasted meat. Maybe some fish. If you want, you can even top it with grated cheese about 15-20 minutes before it's done and eat it by itself. Perhaps some sliced tomatoes with the cheese. Brown sauce goes well with it. If you can bear to leave any, it's pretty good cold on the following day too!