Salt-baked sweet potatoes

I'm mulling over whether to grow sweet potatoes again this year. On the plus side, they were less trouble than I'd anticipated, growing happily under a fleece cloche for most of the summer, even when I forgot to water them quite as regularly as they might have liked. On the minus side, the fleece cloche proved not very durable and were I to grow enough sweet potatoes for more than a few portions, they would take up a lot of space. I'm also wary that they grew well because we had a decent summer; in a more normal, cooler growing season, would it all be worth it?

I think I've decided to give it a go again thanks to a startlingly good salt-baked sweet potato I enjoyed the other day. I first encountered baking in salt with Anna Colquhoun and Mia Christiansen and their salt-baked celeriac.

That celeriac was a revelation: baked whole in a salt paste, the flesh was soft enough to be eaten with a spoon, with an intensely sweet celeriac flavour, salt-spiked at the edges near the skin. It's a bit of show-stopper of a dish: brought to the table still in its salt case and cracked open in front of the diners.

I wondered what other root vegetables might also taste good baked this way and after a bit of trial and error, found that sweet potato is exquisite when cooked in salt: the inherent sweetness of the potato is concentrated and the texture, after three hours in a low oven, is pillowy soft and fluffy.

I had good results with beetroot, too, especially the golden beetroot which are a staple of my allotment, but to get really soft and yielding flesh, it really needs to spend up to four hours in the 

oven. Sweet potato gives you a quicker return for your effort.

The trick is to ensure that the salt paste covers the potato completely: no gaps or holes. The paste needs to be made thick enough to hold its shape so that it doesn't all slump to the bottom of the dish as soon as you put it into the oven, but not so hard as to be un-malleable. As the sweet potato cooks, so the paste will harden into a rigid casing.




Recipe
1 large sweet potato, or 2 medium ones

300g cooking salt
280g plain flour
4 egg whites (this is a great way to use up spare egg whites)
Up to 200ml water

Scrub the sweet potato and dry the skin. Place it on a baking tray and pre-heat the oven to 150 degrees C.

Mix the salt and flour in a bowl and add the egg whites in the middle. Begin to beat together, adding the water a little at a time - you may not need it all. Stop when it's like wet Play-Doh - not thin enough to pour and not too thick to spread with a spatula.

Spread the salt mixture over the sweet potato, making sure the whole of the root is covered. Ensure there is salt paste around the base of the potato, so there are no gaps between the potato and the baking tray.

Put into the middle of the oven and bake for 3 hours. The salt paste will harden and turn brown as it bakes. When you remove it after 3 hours, it should be hard to the touch. Cut the top open with a knife, peel back the skin of the sweet potato and spoon out the flesh to eat.

Untried, untested - this year's new veg

I have my favourites in the kitchen garden, the crops I can’t imagine being without. I can’t imagine tiring of first early Lady Christl potatoes, or the candy-striped Chioggia beetroot, sugar snap peas, cavolo nero or Berrettina Piacentina squash or Sungold and Black Russian tomatoes.

But in other areas I am a lot more fickle. Quite deliberately I look for new veg and new varieties to try each year. It’s part of why I took on the allotment and the luxury of space for experimentation. Last year, I successfully grew ginger (indoors), physalis and sweet onions for the first time and was correspondingly unsuccessful with celeriac; the year before I had a complete 'mare with salsify.

This year’s newbies show a bias towards the new world. It’s partly intentional as I’m developing a Secret Garden Club workshop based on the food from the Americas, so some of the new produce is being grown for harvesting and tasting for the meet-up on September 1st (more info and ticket details here).

Mouse melon, or cucamelon (Melothria scabra)

These very attractive fruits look like stripey grapes and taste, apparently, of cucumber dipped in lime juice. We’re going to grow these in the Secret Garden this year – according to the supplier Suttons Seeds, the plants will climb vigorously, so we’re going to train these up a wigwam made of willow canes and hopefully we’ll be harvesting the fruit from July.

Melon pear

Or Solanum muricantum to avoid potential confusion. I first encountered these fruits which both look and taste like a cross between a  melon and a cucumber about 20 years ago in Chile, where they are called pepinos dulces. I’ve often wished I’d brought some seeds home as the climate in southern Chile isn’t so very different from the climate in northern London, and have been keeping a look out for them ever since. This year I found them in Thompson and Morgan’s catalogue. This is another one to grow indoors, cautiously, to start with and to see if the conditions warrant taking them outside into a sunny sheltered spot – my patio, in this instance.

Sweet potatoes

Although really a sub-tropical plant, cultivars of sweet potatoes (Ipomoea batatas , so related to the morning glory) are being bred to better withstand our cool wet summers. This year I’ve ordered some plug plants of the variety Beauregard to grow in a sheltered spot in the Secret Garden – the supplier, Suttons, claims that this is a better option than the more conventional sweet potato ‘slips’, or cuttings. They’ll need as much warmth as possible, so I’ll cover the ground the black plastic and plant them out through holes cut into it in late spring and cover with a Victorian-style bell cloche. Then we’ll see how the summer goes from there. If it’s anything like last year they’ll stay under cover. And even if they don’t provide much in the way of edible tubers, the young leaves and shoots are apparently also edible and can be cooked like spinach.

Tomato Black Cherry

There are so many tomatoes to choose from that it’s worth trying some new varieties every so often. I’m in a bit of a rut with tomatoes at the moment: Red Alert for early ripening, Brandywine and Marmande for cooking and making passata, Black Russian for flavour; Sungold for eating straight from the plant … Black Cherry looks as it would make a fabulously striking addition to a mixed salad bowl, like a Goth version of Gardener’s Delight. Available from Heirloom Tomatoes and others.

Pak choi Rubi

I can grow great pak choi under cover right at the start of the season, sowing in February or March to harvest in April and May, when, let’s face it, you’re not harvesting much else. After that, I find the slugs and the flea beetles get them, however much I try to prevent it, and also by May/June, lots of other summer vegetables are demanding attention. So pak choi is an early spring crop for me, and the more of it I can raise in that short space of time, the better. With this red version from Nicky's Nursery, I’m looking for a deeper, mustier flavour than the bright spring green of the conventional variety.

After our fantastic results with tomatillos in the Secret Garden last year, I’m going to try these on my rather more exposed allotment, where I’m also going to grow a couple of Szechuan pepper plants this year – more on this they're ready to go out into the ground. We’re also hoping to plant some witloof chicory for forcing in the Secret Garden later this year and I’ll blog more about that on the Secret Garden Club website once we’ve got going with that.