By hand: Place garlic and salt in a mortar, and mash with a pestle to form a paste. Add basil, little by little, pounding and turning the pestle with a grinding motion to form a paste. Slowly add oil, drop by drop, until all the oil has been used and the paste is homogenous. Add salt to taste. Stir again before serving. In a food processor: Place garlic, salt, and basil in the bowl of a food processor, and process to a paste. Add oil, and process again. Add salt to taste. Stir again before serving.Advertisement
Transfer to a small bowl. Serve immediately. The sauce can be stored, covered and refrigerated, for 1 day, or frozen for up to 6 months. Bring to room temperature, and stir again before serving.