Begin by placing the garlic in the mortar followed by the salt and crush them together then what happens is the salt draws out the liquid and it will break down into a purée.
Next add the mustard powder and some freshly milled black pepper really work it in, giving it about 20 seconds of circular movements to get it thoroughly blended.
Now add the vinegar and work it in in the same way and use the pestle to scrape everything down to the bottom of the mortar.
Next add one tablespoon of the oil, switch to a small whisk and give everything a really good, thorough whisk then add the remaining oil a tablespoon at a time whisking thoroughly after you add each spoonful.
Use as soon a soon as possible but whisk it again before dressing the salad.
If you don’t have a pestle and mortar, crush the garlic with the salt on a board using the blunt edge of a knife as we show in our video techniques. (link) Then put the garlic purée in a jar with some freshly milled black pepper and the mustard powder, then add the vinegar and oil and screw the lid tightly onto the jar and give it all a really vigorous shake to combine all the ingredients.
There are many combinations of ingredients you can use to make vinaigrette dressing. One of my favourites is made with sherry and balsamic vinegar.
At any time you can add freshly squeezed lemon juice in place of the vinegar and some of the zest too if you like. I like White Bean and Tuna Fish Salad and Baby Summer Vegetables with Lemon Vinaigrette, which I make with lemon juice, white wine vinegar and light olive oil. See related recipes below.