So what were the strange round dark purple things?
Those, my friend, are Potatoes!
A variety known as Vitelotte. Vitelotte (also called Négresse or Truffe de Chine) is an ancient (quite like an heirloom rose) cultivar of blue-violet potato. Vitelotte potatoes have a dark, almost black skin and dark violet-blue flesh thanks to a high content of the natural pigment anthocyanin. They retain their colour when cooked. The plants mature late and compared to modern varieties produce a fairly low yield. The tubers have a thick skin and thus store well.
Originally from Peru and Bolivia, the Vitelotte variety is still commonly grown there. It is supposed that they are a 200 year old mix of ancient types of Peruvian potatoes. (source: Wikipedia)
Here's a Vitelotte recipe: Vitelotte Potato Chips (crisps, for you UK readers) With Cheddar Cheese.
Wash and cut the Vitelotte unpeeled in thin slices – the thinner the more crispy they get while maintaining their great color. Soak slices in salt water for 5 to 10 minutes, then pad dry.
Deep fry in peanut oil at about 160°C (you can spot little bubbles on a wooden spoon, but the oil should not be smoking). The thinner the slices are, the less time they need to be deep fried. If they start to develop brown patches better get them out quick and drain on paper towels. Try to double deep fry them with a bit thicker slices, and you get an interesting result: they become even more crispy and start to throw bubbles.
Then arrange on a baking sheet and sprinkle some cheese crumbles over the chips. Bake for 2 minutes (or until the cheese melts) at 180°C with additional top grill on. Optionally add some sea salt or other spices to the chips.
So.... what's the next Name This Food! food?