If the British Isles had an official vegetable, it would have to be the potato. After a decade and a half of living here, I think I know just about all there is to know about spuds: how to parboil them before roasting in hot oil or goose fat; how to toss them with butter and chopped curly parsley; how to mash them with milk and butter; and how to bubble-and-squeak them the next day. Not only that, but my Irish mother-in-law Greta is forever lecturing me about the rights and wrongs of preparing "tatties".

But for all the simple beauty of these time-honoured favourites, there is so much more you can do to showcase the potato's versatility and ability to take on other flavours. My beloved Greta may well deem today's recipes as verging on the blasphemous, but they do put her favourite tuber in a fresh context.

Consider, for example, the marriage of chips and ketchup. The reason the relationship endures is that it's never boring. Yes, there's the sweetness of the tomatoes, but there is also a touch of saltiness, bitterness and umami-rich flavour. Now take this sweet element one step farther, and add a few plump prunes and some brown sugar to a tray of roasting potatoes: the resulting caramelisation of the fruit will add an extra sweet note and depth of flavour to any roast bird.

A similar approach can be applied to imaginative effect in a potato tatin, where new potatoes replace the apples, and are layered with a salty element or two such as feta, olives or anchovies. Likewise, try any sweet, soft herb – dill, mint, chervil, chives, say – instead of the more commonly used parsley.

And if it's bitterness or acidity that floats your boat, try dressing new potatoes with lemon-infused oil. One Indian-inspired favourite of mine is mashed potato mixed with lemon juice, breadcrumbs, coriander and chilli, shaped into patties, fried and served with chutney and yoghurt. Not even Greta would object to that.

Iranian vegetable stew with dried lime

Serve this sweet, sharp stew with steamed rice. Serves six.

50g clarified butter

1 large onion, peeled and finely diced

½ tsp ground turmeric

1½ tsp cumin seeds

1 tbsp tomato paste

20g coriander

10g tarragon

10g dill

1kg waxy potatoes, peeled and chopped into 4cm chunks

1 butternut squash, peeled, deseeded and chopped into 4cm chunks

3 Iranian limes, pierced 2-3 times

1 whole green chilli, slit on one side from stem to tip

Salt

5 medium tomatoes, quartered

150g spinach leaves

15g barberries

300g Greek yoghurt (optional)

Heat the oven to 180C/350F/gas mark 4. Put a large casserole dish on medium heat and sauté the butter, onion, turmeric and cumin for 10 minutes. Add the tomato paste and cook, stirring, for two minutes. Tie all the herbs into a bunch and add to the pot with the potatoes, squash, limes, chilli, a teaspoon and a half of salt and a litre of water. Bring to a boil, turn down the heat and boil gently for 15 minutes, until the potatoes are semi-cooked. Stir through the tomatoes, spinach and barberries, crushing the limes gently as you do so, to release some of the juices inside.

Tip into a large roasting tray and bake, uncovered, for 20 minutes, until the sauce has thickened a little and the vegetables are soft. Remove from the oven and leave to sit for five minutes, then serve with a dollop of yoghurt on the side, if you like.

Super-rich white pizza

Yotam Ottolenghi's super-rich white pizza: 'There are few things that are not improved by the addition of a fried egg.' Photograph: Colin Campbell for the Guardian. Food styling: Claire Ptak

Tara, who assists me with recipe testing (among many other things), tells me one of her dad's favourite sayings is, "There are very few things in life that are not improved by the addition of a fried egg." When we tested and retested this recipe, the eggs came, and went, and returned again, so do try an egg-free version, if you prefer. Serves four to six.

500g King Edward potatoes

2½ tbsp olive oil

1 large onion, peeled and finely chopped

10g rosemary leaves, chopped

25g fresh oregano leaves, half of them chopped, the rest left whole

Salt and black pepper

60g anchovy fillets, half of them chopped, the rest left whole

120ml double cream

300g buffalo mozzarella

80g parmesan, coarsely grated

4 eggs (optional)

For the dough

230g strong white flour, plus extra for dusting

1½ tsp fast-action dried yeast

½ tsp baking powder

1 tbsp caster sugar

75ml olive oil

1 egg

100ml lukewarm water

Heat the oven to 240C/465F/gas mark 9. For the dough, put the flour, half a tablespoon of salt, the yeast, baking powder and sugar in the bowl of a free-standing mixer. Using the dough hook, stir on low speed to combine, then add the oil and egg. Stir again and, with the motor running, slowly add the lukewarm water. Mix until the dough comes together (add a little flour if it's very sticky), then remove from the bowl and knead on a lightly floured work surface for three minutes, until elastic and uniform. Place in a bowl, cover and put somewhere warm for an hour; the dough will rise, but not by much.

Meanwhile, put the potatoes in a baking tray and roast for an hour. Remove and, when cool enough to handle, cut them in half, scoop out the flesh in 3cm chunks and discard (or eat) the skin. Put the potatoes in a bowl, toss very gently with two teaspoons of olive oil and a pinch of salt, and set aside.

Put the remaining olive oil in a medium frying pan over a medium-high heat. Add the onion, rosemary and chopped oregano, stir in a quarter-teaspoon of salt and cook, stirring often, for about six minutes, until the onions have softened. Add the chopped anchovies, cook for two minutes, then stir in the cream for a minute and set aside.

Turn down the oven to 230C/450F/gas mark 8. Put two very large baking trays upside down in the oven to heat up, and line two flat baking sheets with baking parchment. Cut the dough in half and roll each half into a thin, 32cm-diameter circle. Transfer to the parchment-lined trays and spread the anchovy mixture over the top, leaving a 2cm border all around the edge. Dot the potatoes on top. Tear the mozzarella into chunks and scatter over, sprinkle over the parmesan and lay on the whole anchovy fillets and half of the whole oregano leaves.

Carefully lift the pizzas (and their supporting parchment paper) on to the hot baking trays. Bake for 10-12 minutes, until they're golden on top and the base is nice and brown; if adding the eggs, crack them on to the pizzas after they've been cooking for eight minutes (you want the whites set and yolks runny). Remove from the oven, sprinkle over the rest of the oregano and serve at once.

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

His new More 4 show, Ottolenghi's Mediterranean Island Feast, starts next Thursday at 9pm.