After more than 10 years in this job, I am seen as some kind of unofficial agony aunt for all things veggie, and in that capacity I am often asked about the appeal – or, more often, the lack thereof – of certain vegetables, and how best to make them tasty. These days, people really seem to want to love vegetables, be that for virtuous reasons or just because vegetables are deemed cool.

This makes me very happy indeed. The trouble is, it is hard to convince people to love all vegetables equally. It is pretty easy to fall for tomatoes and aubergines, peppers, sweetcorn and peas; but many people find it much harder to have the same kind of affection for cabbage and cauliflower, swede, spinach and pumpkin.

My theory, for what it’s worth, is that some of the prevailing attitudes towards these less-loved vegetables have something to do with the fact that they have suffered some unfortunate treatments in the past, and that these unhappy memories have shaped the way we still view them – for instance, the cliched bowl of overcooked, underseasoned, grey and bitter brussels sprouts that sits untouched on the Christmas table. Well, there is nothing fundamentally wrong with sprouts: cooked properly – that is, with care and a bit of zest (quite literally, in many cases) – they are delightful, and certainly no less so even than the ever-popular asparagus or the solid broad bean.

Recently, I have been playing around with some of our less popular vegetables and come up with some remarkable results: I have slow-roasted whole cauliflower heads for hours, basting them regularly with olive oil and butter, which gives them the most delectable smoky richness; I have quickly pickled some cabbage and mixed it with chana dahl, curry leaves and some fine beans (the results featured in this column on 25 October); I made another curry using kohlrabi (definitely not the most popular veg on the block), aubergine, fresh coconut and lime; and I have been serving turnips with so many combinations of spices and herbs that I managed to win over some of the most extreme turnip-sceptics I know. So it pays to put aside preconceived ideas, try some new ways with old vegetables and spread the love.

Roast turnip, potato and garlic with harissa and orange

The natural mellow bitterness of turnips is a wonderful base on which sweet, fruity and spicy flavours can shine. Serve with couscous for a light supper. Serves four.

1kg turnips, peeled and cut into 4cm wedges (880g net weight)

500g waxy potatoes, peeled and cut into 4cm pieces

1 whole head garlic, cloves separated and peeled

½ tsp sweet paprika

1 tsp caraway seeds

1½ tbsp rose harissa (or normal harissa)

Shaved skin of 1 orange

2 tbsp olive oil

Salt

100g watercress

For the dressing

2 tbsp orange juice

1 tbsp lemon juice

2 tsp fennel seeds, toasted and lightly crushed

3 tbsp olive oil

Heat the oven to 200C/390F/gas mark 6. Bring a large pan of salted water to a boil, add the turnips, potatoes and garlic, and boil for six minutes. Drain, refresh under cold water and pat dry.

Put the par-bolied veg in a large roasting tray and mix through the paprika, caraway, harissa, orange skin, oil and three-quarters of a teaspoon of salt. Roast for 40 minutes, turning every 15 minutes or so, until the vegetables are cooked through and have taken on some colour. Remove and set aside for 10 minutes, to cool slightly.

While the vegetables are roasting, make the dressing. Put the citrus juices in a small bowl with the fennel seeds and a quarter-teaspoon of salt, then slowly whisk in the oil until combined.

To serve, spread half the vegetables on a large platter and layer half the watercress on top. Repeat with the remaining vegetables and watercress, drizzle the dressing over the top and serve warm.

Kohlrabi and gorgonzola gratin

The juiciness of kohlrabi gives this a much fresher taste than other gratins, yet it’s every bit as rich and comforting. A bitter rocket, watercress and red onion salad is an ideal match. Serves six.

1 tbsp sunflower oil

1 medium onion, peeled and thinly sliced

300ml vegetable stock

300ml double cream

1½ tsp Dijon mustard

30g parmesan, grated

1 garlic clove, peeled and crushed

8 large sage leaves, finely chopped

Salt and freshly ground black pepper

3 medium-large kohlrabi, peeled and cut into 2-3mm-thick rounds

60g gorgonzola, broken into 1cm pieces

30g panko breadcrumbs

Heat the oven to 200C/390F/gas mark 6. Put the oil in a medium saucepan on a medium-high heat, add the onion and sweat for eight minutes, stirring often, until soft and golden. Add the stock, cream, mustard, parmesan, garlic, sage and a good grind of black pepper. Reduce the heat to medium and cook for four minutes, so the liquid thickens slightly, then take off the heat and set aside.

Spread out the kohlrabi slices on a large board, sprinkle with three-quarters of a teaspoon of salt, then layer them in a large 26cm x 28cm ovenproof dish or casserole pan, slightly overlapping the slices as you go – you should have enough to form about five layers. Pour over the cream and onion mix, making sure a good proportion of the onion and herbs are nicely spread on the top layer of kohlrabi, dot the gorgonzola on top and sprinkle breadcrumbs all over the surface.

Bake for an hour, until the cream has thickened and the top is golden-brown – check the kohlrabi is cooked by inserting a sharp knife: it should easily cut through the layers. Remove, leave to settle for five to 10 minutes, then serve.

Kale and Swiss chard tart

Yotam Ottolenghi’s kale and swiss chard tart: ‘Fantastically delectable and rich.’ Photograph: Johanna Parkin for the Guardian. Food styling: Maud Eden

Don’t be put off by any healthy, virtuous images that may come to mind when you see the name of this dish. This green tart is fantastically delectable and rich. Use spinach instead of chard, if you prefer or can’t find any chard. Serves six to eight.

250g shortcrust pastry

A little plain flour, for dusting

200g kale, roughly chopped

200g Swiss chard, stalks discarded and leaves roughly chopped

2 tbsp olive oil, plus 2 tsp for brushing

30g unsalted butter

1 medium onion, peeled and roughly chopped

2 cloves garlic, peeled and crushed

20g picked tarragon leaves

20g picked mint leaves

30g picked parsley leaves, roughly chopped

40g fresh white breadcrumbs (roughly what you get from a slice of crustless bread)

½ tsp freshly ground nutmeg

100ml double cream

2 eggs, lightly whisked

40g pine nuts, toasted

100g mature cheddar, roughly grated

Salt and freshly ground black pepper

Greek yoghurt, to serve

Heat the oven to 170C/335F/gas mark 3. On a lightly floured work surface, roll out the pastry to about 3mm thick, then transfer to a 24cm round quiche or flan tin. Trim, leaving about 5mm of pastry hanging over the edge of the tin, in case it shrinks during cooking. Prick the base of the pastry all over with a fork, and chill in the fridge for 20 minutes. Line the pastry case with baking parchment, then fill with baking beans and bake for 30 minutes. Carefully lift out the paper and beans, and bake for 10 minutes more, until the pastry is golden-brown, then remove and leave to cool.

Put a large pan of water on to boil. Once the water is bubbling, add the kale and chard, cook for four minutes, then drain and set aside to cool. Transfer the greens to a clean tea towel and squeeze out as much liquid as possible.

Put a medium frying pan on a medium-high heat with the oil and butter. Once the butter has melted, add the onion and fry for six minutes, stirring a few times, until soft and golden-brown. Add the garlic and cook for two minutes, then tip the lot into a food processor. Add the cooked greens and fresh herbs, pulse for 20 seconds, to make a rough green paste and then put in a large bowl. Add the breadcrumbs, nutmeg, cream, eggs, pine nuts, cheddar, half a teaspoon salt and a good grind of black pepper. Mix well, then spoon into the tart shell, spreading it out evenly, then bake for 25-30 minutes, until just set.

Remove and brush with the remaining oil. Leave to cool slightly – for about 10 minutes – and serve.

• Yotam Ottolenghi is chef/patron of Ottolenghi and Nopi in London.

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