I dug up some of my black potatoes Vitelotte today. Blog readers can look back at my post of February 24th this year to see that I bought just 3 tubers of these French potato variety (also known as Black Truffle) on a trip to Borough Market. These have a similar taste, texture and appearance to the pink fir apple varieties. The colour 'bleeds' from the raw tubers in the same way that beetroot do. You must watch your hands and clothing for stains! When cooked they keep a wonderful dark purple colour, although the cooking water was a very bright green, turquoise colour! Taste is delicious, slightly waxy.