For a long, long time I was a purist about gratin Dauphinois both in terms of how I cooked it and when I ate it. As far as I was concerned, it only had six ingredients — potatoes, garlic, milk, cream, salt and pepper (at a push, I’d allow a bit of nutmeg) — and it was a ‘dinner party’ dish, something I made for others not myself, mainly because it was a bit of a faff. But recently I have started fiddling with it, adding other ingredients and, even more interestingly, thinking of it as something I can make just for me, for dinner. Because it isn’t a faff at all really; it’s dead easy. Layer up loads of potato, milk and cream in a dish, flavour it with garlic, or, as I am discovering, with courgette, speck or anchovies, shove it in the oven and, an hour later, one of the yummiest dishes in the world is ready and waiting, requiring barely a salad to embellish it.

The first one I ever made was Delia Smith’s and although I rarely use a recipe now I still swear by her ‘washing the starch off’ tip (more of that later). I always sliced the potatoes in a food processor and, although the result is definitely better, I soon bored of that washing up. Now, having experimented with the horror that is a mandolin, I just use a knife (one of these, if you’re interested). Then, about a month ago I had an adulterated one, in this lovely lovely restaurant and suddenly I realised that perhaps I’d been missing a trick. Who knew that courgette could taste so amazing in a gratin?

When we got back from France I started fiddling, adding a layer of courgette, grated Gruyère and a scattering of breadcrumbs. Next, inspired by the discovery of the Scandinavian dish called Jansson’s Temptation in Jane Grigson’s Vegetable Book, I added some tinned anchovies which gives the potatoes the most incredible savoury flavour and, finally, I chopped up some speck that was in desperate need of eating. Finally I remembered this dish, which is the comfort blanket to beat all comfort blankets, and realised I had subconsciously been aware of this technique for ages. I still think that the best accompaniment to roast chicken or beef is the pure version but the variations are perfect WTF dishes: store-cupboard ingredients, very short method, no standing over a stove. I’m feeling hungry already…

Basic recipe: for two hearty portions you will need

Cupboard (or things you may already have):
butter, for the dish and the top, about 40g
potatoes, 850g
milk, 300ml
garlic cloves, 2
freshly grated nutmeg, a few-goes-on-the-grater-worth
sea salt and freshly ground pepper

Shopping list
double cream, 300ml

Upgrades
courgettes, 2 (but you may not need all of them; see note in method)
tinned anchovy fillets, 8
speck, or smoked bacon/lardons, about 75g
Gruyère, about 40g
breadcrumbs, about 40g

How to (basic method)
1. Preheat the oven to 150°C/130°C fan-assisted/gas 2 and lightly butter a shallow gratin dish.
2. Peel the potatoes, slice them as thinly as you can, then put them into a sink-full of cold water and swill them around a bit. Then put a clean tea towel into a colander and tip all the potatoes into it and wrap them up to drain and dry them off a bit. This is Delia’s idea, which I follow religiously and I think it makes for a much less stodgy gratin.
3. Mix the milk and cream together in a jug with some salt, pepper and a few strokes-of-the-grater of nutmeg.
4. Peel, top and tail the garlic and crush or chop very finely. Add to the milk/cream.
5. Tip the potatoes into the gratin dish and pour over the liquid. At this point you may wonder if your liquid-potato ratio is correct and wonder whether to add more of one of the other. Since your gratin dish isn’t the same as mine here’s how I approach it: the liquid should be lapping at the bottom of the top layer, if that makes sense, but not overlapping it. So you should just see the liquid under the top layer of the potatoes. More than that and it will be too liquid and will most likely bubble over in the oven; less and you might end up with a too-crunchy gratin which is no one’s idea of fun.
6. Dot with knobs of butter, season liberally and bake until done, usually about an hour.

How to: upgrades
If using courgettes: top and tail and slice into thin discs. At step 5. tip half the potatoes into the dish then cover with a layer of courgettes. You may find you have too little or too much (depends on the size of the courgettes) but I find one layer is enough; I tried more once to use the discs up and got a soggy gratin. Cover with the rest of the potatoes and continue as above. I sometimes add some grated Gruyère and a handful of breadcrumbs too before the butter, salt and pepper.

If using anchovies, drain them of their oil and chop the fillets into small pieces. At step 5. tip half the potatoes into the dish then dot the anchovies haphazardly over the top. Cover with the rest of the potatoes and continue as above. Grated Gruyère and a handful of breadcrumbs sprinkled over before the butter, salt and pepper works wonders here too.

If using speck or smoked bacon, again chop it up into small pieces, tip half the potatoes into the dish then dot the speck/bacon haphazardly over the top. Cover with the rest of the potatoes and continue as above. Cheese and breadcrumbs optional, but divine.

For a simple upgrade, make the basic recipe above and then grate Gruyère over the top and/or sprinkle with some breadcrumbs before adding the butter, salt and pepper.