• 90ml (6 Tablespoons) oil
• 30ml (2 Tablespoons) vinegar or lemon juice
• 2.5ml (1/2 level teaspoon) sugar
• 2.5ml (1/2 level teaspoon) mustard (whole grain, Dijon, French, or mustard powder)
• Salt and pepper

Place all the ingredients in a bowl or screw-topped jar and whisk or shake until well-blended. The oil separates out on standing, so whisk or shake the dressing again, if necessary, immediately before use.

The dressing can be stored in a bottle or screw-topped jar for a few months in the refrigerator, but shake it vigorously just before serving.

The proportion of oil to vinegar can be varied according to taste. Here it is in the ratio of 3:1. Use less oil if a sharper dressing is preferred. Wine, herb, cider or flavoured vinegars, or lemon juice, may be used, or use a mixture of half vinegar and half lemon juice.

Contributor's note: From the "Good Housekeeping Cookery Book", Ebury Press.