This is a salad dressing I have made forever. Usually I do not measure anything, so I am also giving visual hints along the way. The one real essential thing is to make this in a wooden salad bowl, I don't know why, but it does make a difference, and even better if you have been making it in the same bowl for years and it is "seasoned".
For the Dressing
1 clove garlic
2 tsp. dijon mustard
2 tsp. worcestershire sauce
1/3 C good quality olive oil
3 Tbs balsamic vinegar
For the Croutons
1 La Brea Bakery Sourdough baguette, sliced into rounds
1/2 cup olive oil
1 tsp. kosher salt
1 tsp. Asian chili sauce
3 cloves garlic, finely minced
1 small bunch fresh cilantro, finely chopped
In a wooden salad bowl, enthusiastically smash a clove of garlic with a fork to release oils, then kick out the pulp.
Whisk into the garlic oil the dijon mustard (I usually use Grey Poupon, but depending on the flavor you are after, you might use something more or less mild.), and Worcestershire sauce. Your "starter" should be a dark brown.
In a thin stream whisking all the while, add the olive oil (I usually use a fairly robust oil as a mild one kind of disappears). What you want to see is the oil start to emulsify, this will take more or less oil depending on humidity, speed of whisking, etc. The oil will get very thick, but there is a tipping point where it will break and become thin and separate. If it breaks, you can all a bit more Worcestershire to bring it back. Your oil, when properly emulsified will be about the color of cafe au lait.
When the oil is nice and thick, whisk in a thin stream the balsamic vinegar, or to taste. Your dressing will now get a darker color. I now pour it out of the bowl into a little pitcher to dress the salad from. I do not clean out the bowl before making the salad, consider it a head start on dressing the salad.
Notes: You can keep this dressing for a couple of days, but it will sometimes break and be more trouble than it is worth to try to fix. And the garlic will get a little wonky if you try to keep it too long.
Usually I use this dressing sort of like a Caesar dressing, cut up romaine lettuce, parmesan cheese, some really good croutons and a couple of vigorous twists of a pepper mill.