Ooh - love celeriac. Rosti - grated, heat butter and a little oil in frying pan until foaming, cook (not stirring) over moderate heat until brown underneath, then squish down all over, and in moderate oven for 20-30 mins until brown all over. Great in coleslaw, mashed, layered with potato and onions and cooked with stock (similar to onebat's recipe ina way); as a root veg in stews...