MAKES ABOUT 1 CUP/240 ML
This classic garlicky mayonnaise-like emulsion sauce, so typical in Catalunya, Valencia, Murcia, and the Balearic Islands, is prepared with the ingredients that make up its composite name: garlic (all) and (i) olive oil (oli). It’s served alongside grilled meats and sausages, many rice and fideo pasta dishes, and even with steamed vegetables. Note that the Spanish spelling has just a single “l”—alioli—and in Murcia and in some other places, some people combine the Spanish words for garlic (ajo) and oil (aceite) and call it ajoaciete instead. In Provence, there is a similar emulsion, aïoli.
Once, cooks prepared allioli in a mortar, mashing the garlic and then, almost drop by drop, incorporating the olive oil, moving the pestle in the same direction and in the same rhythm, until a pale, potent paste was produced. More common now, and much quicker, is using an egg (or egg yolk) to bind the emulsion that is whirred with an immersion hand blender (though a food processor works fine, too). Lighten the sauce by blending equal parts mild olive oil and sunflower oil.
Using an immersion hand blender: In a tall, narrow, and cylindrical container (ideally just wider than the shaft), add—in this order—the garlic, egg, salt, pepper, some drops of vinegar, and the olive oil. While still turned off, place the blender shaft in the bottom of the container. Turn on the blender to three-fourths speed and begin blending. Once the emulsion begins to form, slowly bring the end of the shaft up through the oil and just out, and then slowly back down to the bottom. Bring it up once more and out. Total blending time is 30 seconds to 1 minute. The allioli should have thickened to the consistency of a creamy mayonnaise without any oil pooled on the surface; if not, lower the shaft slowly back down to the bottom and out again.
Using a food processor: Add the garlic, egg, salt, pepper, and some drops of vinegar. Begin whirring the food processor and add in the olive oil in a very slow but steady stream until all of the oil has been used and the emulsion has thickened to the consistency of creamy mayonnaise. Total blending time is about 1 minute.
Transfer the allioli to a bowl. Cover tightly with plastic wrap and refrigerate until ready to serve, for up to 2 days. Just before serving, rewhisk with a fork.