Truly, it is the shock of the blue. When Martin Hamilton first shows you one of his Congo Blue potatoes, you admire the purpley-bluey shine of the skin, and the smooth lustre of the potato. But, then, potatoes with blue skins aren't totally unknown: Arran Victors, for example, have a bluey-purple tinge to them.
It's when Martin cuts into the potato, however, that the shock comes: for the Blue Congo is bluey-purple through and through, an intense lavender-blue the like of which I have never seen before.
And another shock lies in store, for when you cook the Congo Blue, it stays blue: brilliant blue with a translucent blue skin at this stage.
And the taste? Delicious, somewhat floury, with a good strong starchy flavour which is immensely pleasing. Of course, it is still a shock to see a blue potato on the plate as part of dinner, though it does invite curious challenges: we made a champ with red onions instead of spring onions, and purple basil just asks to be chopped and stirred into the Congo Blues along with some chopped sun-dried tomatoes for a bluey-red mash.
For Hamilton, growing the Congo Blues is an amusement, a quirky sideline to the business of being a farmer who grows potatoes and vegetables (and highly-regarded cauliflowers) on 500 acres of farmland, divided between Comber in north Co Down and Killyleagh in south Co Down. "I heard of them from another local grower who had grown them but had then lost the seed, so that was how I became aware of them," he says. Then, when the Glens of Antrim potato producers group, which Hamilton supplies, met with buyers from a supermarket chain, in Northern Ireland, Hamilton suggested growing the Blue Congo to sell in its stores.
The challenge then was to find the seed for the Blue Congo, a task in which Hamilton was assisted by Josie Osborne, a food technologist who works for the Glens of Antrim potato company. It was Osborne who eventually tracked down the seed in Finland.
The potato seems to have first been recorded in the UK around 1900, when it was grown as a curiosity rather than an eater. It is classed as a late main crop potato, but the parentage of the spud is unknown. She points out that the potato remains popular in the US, where it is used to make a red, white and blue potato salad, using red-fleshed varieties such as Red Burgundy to complete the colourful picture. As our delicious recipe from Aisling Chester, of the Olive Tree Company, shows, the Blue Congo is a versatile salad potato which particularly likes the flavour of horseradish.
In the US they also use the Blue Congo to make blue crisps, but I rather prefer the approach of some of the blokes who work on Hamilton's farms. Given the Blue Congos to take home and try, they did what every decent Northerner does when faced with a potato: they made chips. "So, at long last, we have become a blue chip company!" chortles Hamilton.
The aforementioned Aisling Chester is the manageress of Belfast's delightful Olive Tree Company on the city's Ormeau Road. When I mentioned to her that I had come across Congo Blue potatoes, she remembered cooking them when working in restaurants in Australia. Blue Congo Potatoes and Jambon Bayonne on Watercress with Horseradish Dressing and Caramelised Onions is Aisling's version of one of the salads she made back then, a delicious mix of flavours and colours.
Martin Hamilton's Blue Congo potatoes will be sold in Northern Ireland by Safeway stores, at Newtownards and Shore road and Newtownards Road, Belfast. Contact Safeway for details. The Olive Tree Company is at 353 Ormeau Road, Belfast, tel: 028-90648898
Blue Congo Potatoes and Jambon Bayonne on Watercress with Horseradish Dressing and Caramelised Onions
Serves 2
10 small Congo Blue potatoes, washed and gently scrubbed to remove earth
4 wafer-thin slices of Jambon Bayonne or Parma ham
1-2 large onions, sliced finely
about 100ml of a really rich Dijon vinaigrette (as sold in The Olive Tree Company, or use a brand such as Dibbles Classic French Dressing)
About a tablespoon of horseradish relish (look for good brands such as Sourcefoods Organic)
200g watercress Tablespoon finely chopped parsley Olive oil
Sea salt and freshly ground black pepper
Heat a little olive oil in a heavy saucepan. Add the finely-sliced onions and cook slowly, stirring regularly, over a low heat until uniformly golden brown (but not burnt!). This will take about half an hour.
Add about a tablespoon of horseradish relish to the Dijon vinaigrette. Taste and adjust seasoning. You may want to add more relish for a hotter result. Throw in the chopped parsley. Slice the Jambon Bayonne or Parma ham into long thin strips.
Boil the potatoes in the normal way until cooked. They will retain their amazing colour. Peel, and half or quarter. Lightly dress with the horseradish vinaigrette while still warm as they will absorb more flavour. Add the strips of Jambon or Parma.
Pile the watercress in the centre of the plate. Arrange the dressed Blue Congos in the midddle. Finally, arrange the caramelised onions around the outside of the watercress.