You want to make a gratin dauphinois or an onion soup ?

If you want to make a gratin dauphinois or an onion soup, then you need a slicing or filleting knife to cut your vegetables evenly into slices, rounds or strips. But remember that slicing doesn't mean cutting finely or dicing! Try to cut your vegetables in the same direction using a sawing movement, which will provide nice thin, neat slices. Always use a really sharp knife and a good quality chopping board.