Mix together four ounces of the very best mustard powder, four salt-spoons of salt, a large table-spoonful of minced tarragon leaves, and two cloves of garlic chopped tine. Dilute it to the proper consistence by adding alternately equal portions of vinegar and salad oil. It will probably require about four wine-glassfuls or half a pint. Mix it well, using for the purpose a wooden spoon. When done, put it into a wide-mouthed bottle or into little white jars. Cork it very closely, and keep it in a dry place. It will not be fit for use in less than two days.
If you cannot procure tarragon leaves, buy at a grocer's a bottle of tarragon vinegar. Mix it with an equal portion of sweet oil, adding a few drops of garlic vinegar. Then stir in mustard powder till sufficiently thick.