Alioli is the garlic sauce the Catalans claim as their own. This is disputed of course by the French whose aioli is the same sauce found in southern France. Whether French or Catalan, there is agreement on what constitutes authentic alioli: Garlic, olive oil, and salt blended together with a mortar and pestle. Nothing more. Nowadays alioli is more often made with the addition of egg yolk, water and sometimes lemon. Note: Alioli is the Spanish term for the sauce. In Catalan it is called allioli and in French aioli.
True alioli is made in a mortar and pestle, without egg yolks, until it reaches a thick consistency. Alioli masters will demonstrate the perfect consistency by turning the mortar or bowl upside down with the alioli staying in place. Purists believe that the best alioli is made with a mortar and pestle. This is difficult to do. You must first pound the garlic with a little salt until it is completely creamy, and then add the olive oil drop by drop at the beginning, and graduate to a thin stream. Blend the garlic and oil until it thickens. You may want to have a friend on hand and take turns doing this, because it takes a considerable amount of time and muscle.
Alioli is garlic-strong, so you need only a small amount to accompany rice dishes, fish, grilled vegetables such as spring onions, asparagus or artichokes, or grilled meat. Or you can spread it on bread, or even add it to soups. While Patatas Bravas in Madrid, central Spain and Andalucia are accompanied by brava sauce (a spicy pepper sauce) alone, in Catalunya Patatas Bravas are served with brava sauce and alioli. The Catalan version is, in my opinion, far superior to the fiery brava sauce alone version.
There are many recipes for Alioli. I recommend trying the mortar and pestle no egg version at least a few times before making the version with egg yolks. Why? Because eggless alioli is considered the real thing, and if you master that version, and then make the version with egg, you can evaluate whether the "pure" version is worth the effort. I am including recipe links: A video from the CIA Worlds of Flavor Spain Conference, (no egg or lemon) a recipe from Alice Waters, (egg yolk but no lemon) and another from Melissa Clark (NYTimes) using egg and lemon.
I would love to hear about your favorite Alioli recipe, and what you serve it with.
Bon profit! Buen provecho!