So often I'll come across incredible vinaigrettes while eating a salad at a restaurant. I'll ask the staff what is in the dressing and usually they'll respond with some variation of olive oil, vinegar, mustard, garlic, shallots, s/p. I make this type of dressing at home all the time and although it is delicious, it doesn't ever have that extra wow factor that I often experience when eating out.
I've been reading up on umami and some of the most common ingredients being tomato paste, anchovy paste, nutritional yeast, dried porcini mushrooms, fish sauce, parmesan cheese & truffles. I'm going to start experimenting with each of these, but thought I'd also turn to the boards and see if anyone has experience using these (or any other "secret" ingredient) in their dressings and/or a recipe they can share.