Born in Stockholm (Sweden), now live in Sapporo (Japan). Hold a Ph.D. in computer science and work with computers during the days, perform magic in a bar during the nights (and weekends, for kids). Also used to teach historical fencing back in Sweden.
This is (probably) "konnyaku" (コンニャク). It is called "konjak" in English according to Wikipedia. Konnyaku is the name of a plant, and this is used to create a starch based food. It is like a very chewy jello. In Japan, quite a lot of food contains konnyaku. It has close to zero calories and the chewiness of it more or less means you lose calories by eating it.