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.
Intensely fresh basil, raw garlic, grassy olive oil — bright and immediately aromatic
Use a mortar — the crushing action of pestle on stone bruises the basil differently than a blade, producing more aroma and less oxidation Garlic is pounded with salt first — the abrasion breaks down the garlic cell walls and draws out the oils Add basil progressively, not all at once — each addition is worked into the paste before the next goes in Oil is added last, whisked or stirred in to create a rough emulsion Use immediately — pistou oxidises and loses its vivid green colour within 30 minutes
Place the basil in ice water for 10 seconds before pounding — this keeps it colder and slows oxidation A drop of lemon juice helps maintain colour briefly Tomato pistou (with a small amount of very ripe tomato pounded into the paste) is an interesting Niçoise variation For soupe au pistou, the soup should be very hot when the pistou is added — the heat blooms the basil aroma without cooking the paste Pistou also works as a pasta sauce, on grilled fish, or stirred into ratatouille at the end of cooking
Using a blender or food processor — the blade oxidises the basil faster and warms the mixture, dulling the flavour Adding oil before the basil is fully broken down — the paste won't emulsify properly Refrigerating and expecting it to keep its colour — pistou is a fresh sauce that does not hold Using dried basil — utterly wrong for this preparation Adding nuts or cheese to a pistou intended as a traditional Provençal preparation