Cut each clove of garlic in half lengthwise, remove and discard the small sprout inside the clove (if it comes out easily) and transfer the garlic halves to a food processor. Add 1 ½ teaspoons salt and pulse until finely chopped. Add the lemon juice and puree until mostly smooth. Scrape down the sides to clump all the garlic together on the bottom. Let the garlic sit with the lemon juice for 15 minutes to mellow some of the garlic heat.

With the food processor running, slowly drizzle in about 2 tablespoons of the oil through the chute (see Cook’s Note). Stop and scrape the bottom of the processor bowl to mix the oil into the garlic. Turn the processor back on and start adding the oil in a thin drizzle, about ¼ cup at a time, stopping and scraping the bowl after each addition and making sure the mixture stays creamy and emulsified.

After the addition of each cup of oil, add about a tablespoon of ice water (this will help the emulsification and give the sauce a fluffy texture). If at any point the toum looks like it will separate, mix in a little ice water to bring it back together. After all the oil has been added, add 1 to 2 tablespoons more ice water. You should have a thick, fluffy white sauce, similar in appearance to mayonnaise. Taste and add more salt and lemon juice if desired. The toum can be refrigerated in an airtight container for up to 7 days.