The greens have been exceptional this week - tight, squeaky and in rude health. Fat Savoy cabbages, the dew glistening like diamonds in their crinkly leaves; tight bundles of Chinese broccoli with juicy stems as green as emeralds; sprout tops as pretty as a bunch of flowers. I have eaten them three times this week, and each time with rice. The first a bowl of risotto, rich with butter and grated Parmesan, the greens steamed and laid on top. The second, Chinese broccoli with white basmati rice, the grain scented with cardamom pods, Szechwan peppercorns and black pepper. Then, again last night, a meal made of the remains of the risotto, patted into little cakes, given a golden crust in a hot pan and eaten alongside lightly cooked sprout tops.
I like vibrant young greens with the comfort of rice. I like them with ginger and soy or pecorino and butter, or snippets of fat bacon grilled to a crisp. I like them, too, with caraway, cumin, Worcester sauce or sesame oil. Though not all together. And sometimes I eat them with nothing more than a shake of the olive oil bottle, the most peppery I can get my hands on.
Some of my greens come from the farmers' markets, but much is picked up on my weekly trip to London's Chinatown. I frequent this small tangle of shops and restaurants, with their roasted ducks hanging in the windows and baskets of lychees, bok choi and orchids, as much as I can. Who cares that it is only a shadow of its namesake in New York or San Francisco? Rumours of major development plans in this community (the name of a ubiquitous supermarket chain has been mentioned) send a shudder down my spine. Worse still, there is talk that these noisy, exciting streets with their ingrained smell of dim sum and soy sauce may be manicured into a Chinese Covent Garden.
This week there was bok choi as crisp and juicy as I have ever seen it. When it is as good as this you need nothing more than to steam it and toss it gently in hot oyster sauce, chopped garlic and grated ginger. Piled on to brown rice or alongside steamed pork buns, there could hardly be a more straightforward weekday supper. The Thai mangoes are worth picking up too; long and slim with pointed ends, these are the fruits that come swaddled in a little sponge hat to protect them during their shipment. Peel and slice them, or make them into a fruit salad with slices of orange and a drizzle of sweet syrup from the ginger jar.
We shouldn't desert the farmers' markets just because the interesting stuff appears to be over. You will be surprised at just how tempting everything still looks. Which reminds me how beautiful the roots were this week, especially the parsnips. Those long, tapered roots that curl so elegantly and are the very devil to peel, and roast as well as any vegetable you can think of, are intensely sweet, sticky and chewy. One of the prettiest roots of all must be the crisp spheres of kohlrabi. Beautiful, yes, but I am honestly not sure what to say to those of you who have emailed, somewhat hopefully, about what to do with this particular veg. At the risk of asking for trouble from the kohlrabi fan club I must admit this one defeats me. I mean, why in the world you would want to eat anything that smells faintly of gas I just cannot fathom.
But there is so much else worth queuing for. This is gratin weather, and I am not sure that there is much that you wouldn't want to coat in a creamy bechamel and finish with a crisp crumb coating. Cauliflower, natch, but also purple sprouting Jerusalem artichokes (sliced thinly), or long, thin salsify, which often comes with a thick coating of soil, yet once peeled is the most elegant of vegetables (squeeze a little lemon juice over it to stop it discolouring after you peel). But the grooviest gratin in my book is surely the one made from thinly sliced potatoes, cream and garlic, with just the smallest hint of anchovy. I mash the salty little fillets on the chopping board then stir them into the cream and milk, along with salt and black pepper.
Away from the farmers' markets it is the tropical fruits that find their way into my shopping bag. Pineapples certainly, but also the more unusual numbers, like lychees and bags of kumquats. It has taken me quite a while to get the point of this last little fruit, which even at its best seems to be little more than skin and pips. I just pop them in whole and spit out the green seeds as politely as I can. Anyone who wants an orange but can't cope with the fine spray of sticky juice might like to try kumquats instead; at least you can get them in in one go. The pride of the citrus season are the Seville oranges that appear so briefly and almost solely for the pleasure of marmalade makers everywhere. Anyone who has filled their kitchen with the spicy citrus smell of bubbling orange conserve will know they can bring much of the pleasure back every morning as they lift the lid on their proud achievement.
But we shouldn't forget the other January Seville classic - duck a l'orange. This week I bought the plumpest duck ever from my butcher, and for once managed to roast it so that its breast stayed sweetly moist. A little sauce on the side made from onion, carrot and celery, stock, grated Seville orange zest (if the oranges are very bitter then I use only one or two of these, with the bulk made up with the 'ordinary' Spanish oranges), a dash of Grand Marnier and the juice and zest of a couple of Sevilles is enough to make you wonder why this dish has fallen so dramatically from grace. It's one I look forward to every year.
The only sad part about it is that after several years of eating roast duck I have to finally admit that even the biggest, fattest, most waddly duck is really only a meal for two. There is always a temptation to get a third portion out of it and it is always a mistake. Better a feast for two with a bit left over for cold than a squabble between three.
Those who have ever made Peking duck may wonder if there is any other use for the bits of crisp skin still left on the carcass. This is where the frugal cook wins head over heels over the extravagant one. That skin is wonderful when crisped up a bit under the grill and tossed on top of a crisp salad of winter greens. The fat that runs from the duck can be used as a dressing for a salad of orange, duck skin and watercress, or perhaps Belgian chicory and frisee. And as for those delicate, floury little pancakes, have you ever tried stuffing them not with duck, but with roast pork that you have seasoned with fennel seed and a little soy instead? Utter bliss.
There, I've ended the week as I begun it, shopping in Chinatown.
· Nigel Slater returns in three weeks