Pistou
Provence, France — particularly Nice and the Var; related to but distinct from Ligurian pesto
Pistou is Provence's version of pesto — a raw paste of fresh basil, garlic, and olive oil, made without pine nuts and without cheese (at least in its traditional form). The word comes from the Provençal 'pistar', meaning to pound, which is how the original was made: basil leaves and garlic crushed in a mortar until they form a paste, then emulsified into olive oil.
Pistou's function in Provençal cooking is primarily as a stirred-in finishing sauce for soupe au pistou — the summer vegetable soup that takes its name from this condiment. A bowl of the soup (made from haricots, courgette, tomato, pasta, and whatever is in the garden) is served, and a large spoon of pistou is stirred in at the table. The raw basil and garlic perfume the hot soup dramatically without cooking — the contrast between the long-cooked vegetables and the raw paste is the dish's central pleasure.
Pistou differs from Ligurian pesto not just in the absence of nuts — the basil used in Provence is often a larger, more anise-forward variety than the small-leaved Genovese basil, and the character of the olive oil (fruitier in Provence than the grassy oils of Liguria) changes the sauce's flavour profile.
Modern pistou sometimes includes a little tomato (an Niçoise addition) and sometimes a small amount of hard cheese, but the purists insist it needs neither.