A gratin is a baked dish with a topping of grated cheese, breadcrumbs or egg. This one consists of slices of potato in a cream, cheese and mushroom sauce. This recipe is delicious as a vegetarian main course, or can be used as the potatoes to accompany a meat course. There's both cream and cheese in it, so it's not healthy enough for every-day use, but it's perfect for a delicious occasional treat.

The gratin can be prepared in advance, kept in the fridge for a few hours, and then bunged in the oven, giving you time to chat with your guests or prepare other courses.

This recipe serves four.

Ingredients and Equipment

• oven proof dish, about 30cm × 24cm and at least 6cm deep (12in × 8in and 2½in deep)
• aluminium foil
• 1kg of potatoes (2.2lb)
• 20-30g (about 1oz) of dried porcini mushrooms, also known as cèpes or boletus
• 150ml (5 fl oz) boiling water
• teaspoon (5ml) of salt
• 220g (½lb) mushrooms (any sort, but normal shop-bought field mushrooms will do)
• a little oil for frying
• 150-200g (5-7oz) grated cheese
• 125ml cream (4-5 fl oz)

Method

• Break up the dried mushrooms into small pieces and put them in a measuring jug. The easiest way is just break them up with your fingers, but you can use a knife for the more troublesome ones.

• Pour on the hot water, topping up to 150ml, and add the teaspoon of salt. Leave the mushrooms to soak while you're doing the rest of the preparation.

• Slice the fresh mushrooms and fry them in a little oil for a few minutes so that they begin to turn brown and don't look completely raw. Remove them from the heat.

• Peel the potatoes and slice them to a thickness of about 2.5mm (one eighth of an inch). That's about the thickness of a euro coin. [Contributions welcome as to what coins it compares to in your country.]

• Preheat your oven to 200°C (400°F).

• Assemble the gratin in the oven-proof dish in layers. Use a quarter of the potato and a quarter of the cheese per layer, but one third of the fried mushrooms. You need to put a layer of potatoes, then mushrooms and grated cheese, then repeat for a second and third layer. Top it off with a fourth layer of potato. If you've potato left over, it's best not to use it; making the gratin too thick will prevent it from cooking properly.

• Pour the cream into the jug with the dried porcini and then pour the mixture over the top of the gratin.

• Sprinkle the last of the cheese over the top.

• Cover with aluminium foil. At this stage you can store it in the fridge until later, or cook it straight away.

• Bake the gratin for an hour covered with the foil. Then remove the foil and bake for another 15 minutes. Test the potatoes with a fork - if the fork slides in, they're done. Otherwise you might need another 15 minutes.

If you're eating this as a vegetarian main course, you should serve it with a green salad. Enjoy!

Notes

The slicing of the potatoes can be done with a large, sharp knife, but this is quite time-consuming, particularly if your knife skills aren't up to much. This job is made a lot easier if you use a 'mandoline slicer', which reduces the slicing part of the preparation to a couple of minutes. If you make this dish often, it's worth getting one of these.

When choosing potatoes for the gratin, the bigger the better.

Organic potatoes really will taste better, but you have to be prepared to throw out a few that have gone bad inside.