Have you ever tried whitecurrants? I bet you haven't.

Even I, until today, had never tried whitecurrants, and I've tried a lot of weird and obscure fruits and vegetables. I bet you go your entire life without ever seeing whitecurrants in the supermarket or market; in fact, you may never see them in the flesh at all, unless you're lucky enough to spend a lovely couple of hours at a pick your own farm that has them (and even then, space is usually devoted to the more popular red and black varieties). Or, of course, unless you're lucky enough to have a PhD supervisor who frequently bestows her home-grown fruit and veg on you.

She referred to them as 'a challenge', and it's not hard to see why. You can't exactly pick up a cookbook and find a selection of recipes for whitecurrants. The only recipes I've ever seen are in a tiny chapter devoted to the fruit in Nigel Slater's Tender Part II. Even there, he remarks upon the sourness of the currants and therefore their difficulty as happy bedfellows with other ingredients. There is, though, a luscious-looking whitecurrant tart that I have my eye on, with a ginger biscuit crust and a fromage frais and cheese filling.

We don't really seem to 'get' currants in the UK. You can sometimes find them at markets and supermarkets in summer, but only for a very brief period of time, and no one really seems to know what to do with them. They do present a problem, being fiddly to remove from their stalks and, to some tastes, unpleasantly sour. The trick, I find, is to couple them with sweeter fruits: redcurrants are lovely with peaches, for example, or strawberries, and blackcurrants work well with apricots, pears and apples. If you're looking for a reliable supply of these treasures, pick your own farms are probably your best bet, or growing your own (or, as I did, accidentally but conveniently choosing as your supervisor someone who grows their own).

Whitecurrants, though, are the most elusive of the lot. While redcurrants can be found, fairly reliably, in the summer, and blackcurrants do usually make an appearance in some supermarkets, whitecurrants are just not cool in the world of currants, apparently. Maybe it's their lack of bright colour, unlikely to catch the capricious eye of the passing supermarket shopper. Maybe it's their intense sourness, an acquired taste. Maybe it's a vicious circle: the less we see these currants, the less we know what to do with them, therefore the less likely we are to buy them.

So why bother with these little globes of sourness? Because, as you can see, they are totally gorgeous to look at. Up close, they have an eerie translucency to them; you can just make out the seeds inside, while the skins have a pearlescent sheen. They are not really white, but myriad shades of cream, jade, beige, almost giving off a muted glow as they sit in a bowl, waiting to be made use of. They really do look like a string of culinary pearls, begging to adorn your food in the way you might use pomegranate seeds or dried cherries. And food, in my opinion, should be adorned. Even if it's just a scattering of bright herbs, it can make all the difference.

Given their sourness, whitecurrants need to be paired with something very sweet - my thoughts initially turned to cheesecake and meringue. However, I then considered their potential in savoury recipes. Sour ingredients - those that spring to mind are gooseberries and rhubarb - are often combined with fatty meat or oily fish, their astringency used to balance the richness of the protein. Always one to go for oily fish over pretty much any form of meat, I just had to choose the best oily fish of all: mackerel.

The sour nip of a whitecurrant works perfectly with the moist, rich, crispy-edged flesh of a seared mackerel. The combination is unusual and refreshing, surprising with every mouthful. To make the mackerel even more flavoursome against the currants, I coated the fillets in a mixture of lemon salt (I'd really recommend this if you don't have any; it's just salt mixed with dried and ground lemon peel, and you can get it from JustIngredients online) and smoked paprika. It's an incredibly flavoursome, moreish combination: smoky and salty with an addictive tang from lemon. I think I might always cook mackerel in this way now; it works with so many accompaniments, and it really brings out the intense character of the fish.

To go alongside, a salad of whitecurrants and lentils. This is basically taken from Nigel Slater's Tender, where he suggests serving it with the leftovers of a roast. It works so well with my mackerel idea, though, that I don't think you could find a better combination. The lentils are nutty and earthy, a pleasant canvas for the other dancing flavours, while the burst of sour juice from a currant peppers each mouthful. There is freshness and zip from masses of shredded parsley and mint, and finally that gorgeous, succulent, crispy-skinned spiced mackerel.

If you can't get whitecurrants, you could make this with redcurrants, or pomegranate seeds, or even dried sour cherries or raisins at a push. If you don't like or have mackerel, use trout or salmon, or go the meat route - smoked chicken, sausages, roast pork, lamb and game will all work well. If you're vegetarian, try it with some crumbled goat's cheese and toasted walnuts or pecans. Either way, you'll be rewarded with a simple but beautiful plate of food, packed with nourishing and delicious vibrant flavours.

And, of course, garnished with a string of pearls.

A big thank you to Trev for the gift of whitecurrants - I hope you approve of what I did with them!

Smoky spiced mackerel with whitecurrant and lentil salad (serves 4):

400g puy lentils
Water
Sea salt
6 tbsp olive oil
2 tbsp cider or white wine vinegar
Freshly ground black pepper
A small bunch of parsley, finely chopped
A small bunch of mint, finely chopped
200g whitecurrants (or redcurrants if you can't find whitecurrants), stalks removed
4 mackerel, filleted (to get 8 fillets)
3 tsp lemon salt
3 tsp smoked paprika
Olive oil, for cooking

Cook the lentils in plenty of boiling, salted water for about 15 minutes until tender but still nutty. Drain and return to the pan. Mix the olive oil and vinegar with a teaspoon of salt and some black pepper, then stir into the lentils while still warm, along with the herbs. Allow to cool a little, then gently stir in the whitecurrants. Check the seasoning - lentils need quite a lot of salt to make them sing.

For the mackerel, dry the fillets on kitchen towel. Mix together the lemon salt, paprika and some black pepper, then spread over the fillets. Heat a glug of olive oil in a non-stick frying pan, then sear the mackerel on both sides over a high heat for about 2 minutes each side (you may need to do this in batches if your pan isn't big enough). Serve on top of the lentil salad, garnished with a little extra parsley.