Soupe au pistou is the great summer vegetable soup of Provence — a vibrant, garden-fresh potage of white beans, green beans, courgettes, tomatoes, and pasta, served with a pungent basil and garlic paste (pistou) stirred in at the table. This soup is the French cousin of Italian minestrone, its Provençal identity defined entirely by the pistou — the word deriving from the same root as pesto (pestare, to pound) — which transforms a simple vegetable soup into something extraordinary when stirred through at the last moment. The soup itself requires summer-ripe vegetables: soak 200g of dried white beans (coco or borlotti) overnight and simmer until nearly tender, about 45 minutes. In a separate large pot, sweat diced onion, leek, and celery in olive oil for 10 minutes. Add 2 litres of water (not stock — the purity of the vegetables should speak), the drained beans with their cooking liquid, diced carrots, and diced potatoes. Simmer 15 minutes. Add diced courgettes, cut green beans, diced tomatoes (peeled and seeded), and small pasta (coquillettes, macaroni, or broken spaghetti). Cook a further 10-15 minutes until the pasta is al dente and the vegetables are tender but retain their identity. Season with salt and pepper. Meanwhile, prepare the pistou: pound 3 large garlic cloves with coarse salt in a mortar until smooth. Add 60g of fresh basil leaves and pound to a vivid green paste. Work in 80g of finely grated Parmesan and drizzle in 100ml of best Provençal olive oil in a thin stream, pounding continuously, until you have a thick, aromatic paste that perfumes the entire kitchen. Do not use a blender — the mortar produces a texture and flavour release that machinery cannot replicate. Serve the soup in wide bowls with a generous tablespoon of pistou in each, to be stirred through by the diner. The heat of the soup releases the basil's volatile oils in a heady rush. Offer extra pistou and grated Parmesan at the table. This is high summer in a bowl — no meat, no stock, just vegetables at their peak and the transformative power of basil, garlic, and olive oil.
Water, not stock — let vegetables speak for themselves. Vegetables added in stages by cooking time for even doneness. Pistou pounded in mortar, never blended — texture matters. Pistou stirred in at the table, never cooked — heat releases volatile oils. Summer-ripe vegetables are non-negotiable for authentic flavour.
In Provence, the soup is often made the day before and reheated — the flavours deepen overnight, and fresh pistou is added at serving. Fresh shell beans (cranberry, flageolet) in season are infinitely superior to dried. A Parmesan rind simmered in the soup adds subtle umami depth. If basil is truly magnificent, increase the quantity without hesitation — this is a basil delivery system as much as a soup. The pistou without cheese is equally valid and more traditionally Niçois.
Adding pistou during cooking, which destroys the basil's volatile aromatics and turns it brown. Using stock instead of water, which overwhelms the delicate vegetable flavours. Overcooking the vegetables into a mushy homogeneity — each should retain identity. Using a blender for pistou, which heats and oxidises the basil. Skipping the mortar step for garlic, leaving raw chunks instead of smooth paste.
French Regional Cooking — Anne Willan