Grate off the skin of long squash (the kind that looks like cucumbers), cut the squash in slices, one-quarter of an inch thick, and fry in olive oil; prepare a sauce with a little vinegar, one-half teaspoon of prepared mustard, two tablespoons of olive oil, beat these ingredients very well; add two shallots or leeks, cut in small pieces, pour sauce over the squash and serve.