Yotam Ottolenghi’s mushroom and walnut galette. Photograph: Louise Hagger for the Guardian. Food styling: Emily Kydd. Prop styling: Jennifer Kay

Walnuts are the second most popular nut in the world, after almonds. In my kitchen, however, they are second to none.

The short season for young, fresh “wet” walnuts is upon us, and few things give me as much pleasure as cracking open the hard, dry shell of a newly-picked nut to reveal that moist, pale kernel inside. Its texture is yielding, not crisp, and its flavour milky-sweet. Rather than cooking with them, these nuts are best eaten as they are, with cheese or fruit, or added to a simple salad. For cooking and baking, you want the crisp snap of year-round dried walnuts. These are kiln-dried, which draws out their nutty, tannic flavour. They can then be crushed, toasted, blitzed, chopped and caramelised for all sorts of soups, pastries, salsas, salads and dips.

You should taste most raw ingredients before you use them, and in the case of shelled walnuts, it’s essential you do so. However grateful you are that you’ve not had to break open all those shells, the difference between a batch of good walnuts and rancid ones will make or break an entire dish.

Mushroom and walnut galette

I’d be tempted to slip some goat’s cheese in between the mushroom layers here. And if you fancied doing without the pastry, the paste and fried mushrooms are lovely on crusty bread, too. Serves four.

For the walnut pastry
50g walnut halves, lightly roasted
190g plain flour
Salt and black pepper
60g unsalted butter, fridge-cold and cut into 1cm dice
2 egg yolks, plus 1 egg lightly whisked, for the glaze

For the mushroom paste
1 tbsp olive oil
1 small leek, trimmed and finely sliced
2 portobello mushrooms, chopped
70g button mushrooms, finely sliced
1 garlic clove, peeled and crushed
1 tbsp picked thyme leaves
5g dried porcini mushrooms, soaked in 100ml boiling water for half an hour
60g cream cheese

For the fried mushrooms
2 tbsp walnut oil
1 portobello mushroom cut into 2cm-wide wedges (65g)
50g button mushrooms, cut into 0.5cm-thick slices
180g mixed wild mushrooms, torn apart or cut into 0.5cm-thick slices, depending on variety
40g spinach, roughly shredded
1 tbsp dill, roughly chopped
1 tbsp tarragon, roughly chopped

First make the pastry. Put the nuts and flour in a food processor with a quarter-teaspoon of salt. Blitz until the nuts are fully broken up, then add the butter and blitz again until the mixture is the consistency of fine breadcrumbs. Add the egg yolks and two to three tablespoons of cold water, and work the pastry until it starts to come together. Transfer to a medium bowl and knead until the dough forms a ball. Shape into a disc, cover with cling-film and refrigerate. Remove from the fridge 10 minutes before using.

For the paste, heat the oil in a large saute pan on a medium-high flame. Once hot, add the leek, portobello and button mushrooms, garlic, thyme and a third of a teaspoon of salt. Fry for five minutes, stirring a few times, then add the soaked porcini and their liquid (strain this through a cloth or fine-mesh sieve first). Cook for two minutes more, until the mix is quite dry, then transfer to the food processor and blitz smooth. Add the cheese, blend again to combine, then tip into a small bowl.

Heat the oven to 200C/390F/gas mark 6. Put the walnut oil in a large frying pan on a high heat, then fry all the mushrooms, a quarter-teaspoon of salt and plenty of pepper for nine to 10 minutes, stirring a few times, until golden-brown. Take off the heat and stir in the spinach and herbs.

On a large square of baking paper, roll out the pastry into a 25cm-diameter circle just under 0.5cm thick. Carefully transfer the pastry and its paper base to a large baking tray and spread the mushroom paste over the top, leaving a 3cm clear rim around the edge. Top with the fried mushrooms, then lift the sides of the pastry circle up and over the mushrooms. Pinch the pastry together at 2cm intervals, pressing down on the mushrooms so they are partially encased. Don’t worry if the pastry breaks up a little: it will still be fine. Brush the pastry with eggwash and bake for 20 to 25 minutes, until cooked and golden-brown. Remove, leave to rest for five to 10 minutes, and serve.

Salsify and roast cauliflower with lemon mayonnaise and walnuts

Salsify is a long, slim root with a dark skin and creamy-white, slightly sweet flesh. Buy it from good grocers, but jerusalem artichokes, waxy potatoes or celeriac take very well to this treatment, too. Serves four.

1 medium cauliflower, trimmed and separated into 5cm florets
2 tbsp olive oil
Salt and black pepper
8 salsify, trimmed, peeled with a potato peeler and cut into 5cm-long pieces
1 lemon, quartered lengthways and deseeded
40g unsalted butter
40g shelled walnuts, roughly broken
5g picked thyme leaves

For the mayonnaise
1 egg yolk
¼ tsp wholegrain mustard
1 tsp Valdespino sherry vinegar (or other top-quality sherry vinegar)
150ml sunflower oil
1 tsp lemon juice

To make the mayonnaise, whisk the egg yolk, mustard and vinegar in a medium bowl with an eighth of a teaspoon of salt, then slowly add the oil in a gradual stream, whisking all the while, until the mix emulsifies and goes thick. Whisk in the lemon juice, cover and refrigerate.

Heat the oven to 220C/425F/gas mark 7. Mix the cauliflower with the oil, a quarter-teaspoon of salt and plenty of pepper, spread out on a 20cm x 30cm oven tray lined with baking paper, and roast for about 12 minutes, until just cooked and golden brown.

Meanwhile, bring a medium pan of salted water to a boil, cook the salsify for seven minutes, until tender, and drain.

Put a small frying pan on a high heat and, once hot, add the lemon wedges. Sear for two minutes, turning after 60 seconds, so they char on both cut sides, then set aside. Melt the butter in the same pan and, when it starts to brown after 90 seconds or so, fry the nuts, thyme and an eighth of a teaspoon of salt for just 30 seconds, then tip into a bowl, to stop them cooking further.

Divide the warm salsify and cauliflower between four plates, spoon over the warm, buttered walnuts and serve with a spoonful of mayo and a lemon quarter.

Saffron and ginger pears with chocolate sauce and walnut brittle

Yotam Ottolenghi’s saffron and ginger pears with chocolate sauce and walnut brittle. Photograph: Louise Hagger for the Guardian. Food styling: Emily Kydd. Prop styling: Jennifer Kay

You can make the pears a day ahead, but if you do, reduce the syrup a second time, because the fruit will keep releasing juices. Serves four.

4 ripe williams pears
200g caster sugar
¼ tsp saffron
4cm piece fresh ginger, peeled and cut into 2mm slices
90ml double cream
70g 70% cocoa solid dark chocolate, chopped up

For the brittle
30g shelled walnuts
30g caster sugar
1 pinch flaked sea salt

Peel the pears, but leave the stalks intact. Using a small, sharp knife, cut a 2cm circle around the base of each pear, push the knife about 3cm inside, and remove as much of the core and seeds as possible.

Pour 1.2 litres of water into a medium saucepan and add the sugar, saffron and ginger. Bring to a boil and, once the sugar has dissolved, add the pears (they should be just covered, so add boiling water if need be). Turn down the heat to medium and simmer for 10-15 minutes, depending on the ripeness of the pears, until a sharp knife goes in without any resistance. Take off the heat and leave to cool for an hour (the fruit will take on the colour of the saffron during this time). Lift out the pears, return the syrup to a high heat and reduce for 30-40 minutes, until you are left with about 220ml of thick syrup in the pan. Strain this over the pears and set aside. Take 10g ginger from the sieve and finely slice; discard the rest.

To make the brittle, put the nuts and sugar in a small saucepan on a medium-high heat for three to four minutes, shaking the pan regularly, so the nuts don’t catch and take on too much colour while the sugar melts to a dark caramel. Spoon on to baking paper, sprinkle with salt and leave to cool and harden. Once cold, chop into 0.5cm pieces.

Pour two tablespoons of syrup and the cream into a small saucepan and bring to a simmer. Add the chocolate, take off the heat and wait a minute, for the chocolate to melt, then stir to combine.

To serve, stand a pear upright in each of four small shallow bowls. Pour a tablespoon of syrup over each pear, then spoon a quarter of the chocolate sauce over one side of each fruit (it looks much better if you keep one half uncoated). Sprinkle the sliced ginger and brittle over the top, and serve.