I have a friend who uses no other recipe books than those of Elizabeth David and Jane Grigson. They offer more than enough to keep one occupied. Their books were written from the points of view of domestic cooks, and have a simplicity lacking in today's glossy cookbooks, mostly inspired by ideas from professional kitchens.
You have to be wary only of Elizabeth David's measurements, and of Jane Grigson's use of butter. In this celeriac gratin, Grigson dots butter in between the layers, and on top. I have left it out.
This will provide a light supper for two, with perhaps some rice or a salad.
Peel a medium celeriac. This is a crude job, because the vegetable is so knobbly; I cut it in half, then cut off the skin with a knife, accepting that some of the flesh will get lost too. Cut it into slices about 0.75 cm thick; you can drop them into acidulated water to prevent discolouration. Steam until soft.
Make a tomato sauce: soften a chopped clove of garlic in a tbsp of olive oil, tip in a can of tomatoes, add a little salt, and simmer until thick. You can break up the tomatoes with a wooden spoon as they cook. I sometimes add a little vinegar and sugar, and maybe a bayleaf.
The sequence in which you layer ingredients in a gratin is not terribly important. This is what Grigson recommends here. Butter a gratin dish, and layer the celeriac with grated parmesan, grinding over pepper if you like. Finish with a layer of celeriac. Pour the tomato sauce over the top. Over the top of that, sprinkle a mixture of breadcrumbs and parmesan (about 1 tbsp of each). Bake at gas mark 5/190 C for about 30 minutes, or until the topping is brown.
These layers of celeriac are not complete. I had three layers; but there were plenty of gaps between them.