rouille

Rouille is a garlicky, saffron-spiced emulsified sauce from the Provence region of France, most closely associated with bouillabaisse, a traditional Provençal fish stew, and with soupe a l'oignon in some kitchens. The name derives from rouille, meaning rust, in reference to the sauce's orange-red color.

Traditional rouille is made by pounding garlic with bread (often stale crusts) that has been softened in water or fish stock, then gradually emulsifying the mixture with olive oil. Many recipes include saffron or a saffron infusion for color and aroma, and some add red pepper or hot chili to provide heat and a characteristic hue. Eggs are sometimes added to help with emulsification, yielding a mayonnaise-like texture; many older or regionally minded preparations omit eggs for a lighter, egg-free sauce. Seasonings typically include salt and a splash of vinegar or lemon juice.

Preparation methods vary: mortar and pestle, blender, or whisking by hand. The result is a thick, creamy garlic sauce that can be spread on crusty bread or stirred into bouillabaisse to enrich the broth.

In addition to its role with fish stews, rouille appears in regional Provençal and Mediterranean cuisines as a cousin to aioli. Variations exist between towns and households, but the core ingredients remain garlic, olive oil, bread, and saffron-tinted color.