We had the first frosts this week. Well, the first ones in London. And, though it was wonderful to wake up to such bright, sharp cold, it made me realise how lucky we have been with the weather this autumn. Nothing but crisp, sunny days, barely a trace of rain, and plenty of leaves to crunch. Now, though, it might be time to buy some new gloves and to succumb to real comfort food. Soup and toast are no longer going to cut it.

For me, there is nothing more comforting than some kind of hot potato dish, whether mashed, roasted or baked. My personal favourite is dauphinoise potatoes because they always feel like a treat, yet they are one of the most straightforward shove-in-the-oven dishes about. You can eat them on their own, with some salad or with a roast, make them into a meal by adding some smoked mackerel or, for a vegetarian and very-low-on-shopping version, this one, using dried porcini, is a delight.

The recipe comes from the second book in my library haul of joy this month, River Cottage A to Z: Our Favourite Ingredients and How to Cook Them. Written by seven River Cottage experts, including Hugh Fearnley-Whittingstall, Gill Meller, Mark Diacono, Nikki Duffy and Pam Corbin, all of whom are successfully published in their own right, this is a bit like getting seven books or approaches for the price of one. It is an encyclopedia in the true sense of a word: over 700 pages long and with 300 entries on different ingredients, each one is explained in a thorough but not overwhelming way, and then there is a recipe or two to go with it.

I have been reading it from front to back, for a couple of weeks, over lunch and though I haven’t got very far everything I have cooked, including this step-up-from-the-usual dauphinoise, exemplifies the River Cottage approach: here’s something lovely, here’s how easy it is to make. In this instance, just by adding some dried porcini, dauphinoise potatoes become either a really dressed-up side or a very good vegetarian main. The mushrooms add a real depth of flavour, yet somehow cut through the heaviness of the potatoes and the whole thing will warm you through for several hours. I’ve had it once this week, I am planning a second outing and I fully expect to gain as much weight as this massive and unmissable book by the spring…

Potato and cepes dauphinoise (adapted from River Cottage A to Z: Our Favourite Ingredients and How to Cook Them)

Makes enough for 2-3

Cupboard (or things you may already have)
butter, 15g plus a little extra for greasing
garlic clove
floury potatoes, 500g
fresh nutmeg
sea salt and freshly grated black pepper

Shopping list
dried cepes/porcini, 15g
hard cheese (not Cheddar), like Berkswell or Parmesan, 50g
double cream, 200g

How to
1. Preheat the oven to 160°C/140°C fan/gas 3.

2. Soak the dried cepes/porcini in boiling water for 10 minutes.

3. Whilst the cepes are soaking, butter a small-ish gratin dish (big enough to serve 2-3, not a family-sized one), peel and crush the garlic, peel and slice the potatoes then grate the cheese.

4. Put the garlic, potatoes and cheese into a bowl. Add the cream, grate over the nutmeg, season then toss well to make sure all the potatoes are covered in cream.

5. Drain the cepes, reserving the liquid if you can/want (it can be used in soups or stews) then squeeze them gently with your hands to remove any excess water.

6. Add the mushrooms to the potatoes and mix in gently to make sure they are well distributed.

7. Tip the mixture into the dish, scraping out any remaining cream or cheese from the bowl onto the potatoes, and flatten the layers down with the back of a spoon. Season with a little more salt and pepper, dot with butter then bake for about 1-1½ hours, pressing down on the top with a spoon every so often, if necessary, to make sure the potatoes are still in the cream and don’t get too dry.

8. The potatoes are done when they are golden brown and bubbling and a fork goes into them easily.