First, how I was taught in France...
Put a heaped teaspoon of Dijon mustard in your salad bowl. Add about 2 tbsp red wine vinegar. Mix the mustard and vinegar together until the mustard has 'dissolved into the vinegar. This is the most important step - to mix the mustard into the vinegar before you add the olive oil.
Add a big pinch of salt, a big pinch of pepper, and about 4 tbsp olive oil. Mix thoroughly so that vinegar and oil are fully incorporated.
The reason you add the vinegar first is that the mustard doesn't break down if you add it to the oil first, and the mustard is what makes the dressing emulsify.
Taste and adjust to taste - too vinegary = add more oil, too oily = add more vinegar etc.
Add your washed salad and toss in the seasoned dressing.
Now how we make it at home...
First find yourself a small jam jar with a lid that seals really well (you don't want oily dressing flying around the kitchen when you giving it a really good shake). Our jar is one from France with a snap on lid that used to have Dijon mustard in.
Add all ingredients in the order above, but just put the lid on and give the jar a really good shake instead of mixing with wooden spoon.
We sit the jar on a saucer with a teaspoon for people to add as much or little dressing to their salad as they like. If you don't use it all it keeps in the fridge with the lid on for at least a week.
Once you have mastered making a thick unctuous dressing trying experiment with different ingredients;
- Different vinegars - balsamic, raspberry
- Different mustards - Wholegrain mustard (try 1 tsp Dijon + 1 tsp Wholegrain) or English mustard (unsurprisingly quite strong!)
- Different oils - Walnut oil (1/2 walnut + 1/2 olive oil as walnut on it's own is a bit too much)