Pre-heat your oven to 230C/ gas 8/ fan 210C. Peel the celeriac, slicing off the top and bottom and sweeping down the sides with a heavy, sharp knife to remove the tough skin. Cut the celeriac into thumb-thick slices and then into fat chips.
Bring a very large saucepan of salted water to the boil, throw in the chips and blanch (boil rapidly, uncovered, for 1-2 minutes). Drain the chips and throw back into the saucepan. Add the oil, curry powder and sea salt. Toss until well coated.
Spread the chips over a large heavy baking sheet, leaving plenty of space (you may need 2 sheets). Cook them in the oven for about 30-35 minutes.