1 head fresh garlic (squeeze it: it should be solid and very firm)
1 teaspoon kosher salt
Juice of 1 lemon
1 3/4 cups (420 mL) neutral oil, such as safflower or canola
4 to 6 tablespoons (60 to 90 mL) ice water
Peel the garlic cloves and slice them in half lengthwise. If there is a green germ in any of the cloves, remove it to prevent the bitter, burning flavor it imparts.
Process the garlic cloves with the salt in the food processor, stopping and scraping down the sides a few times, until the garlic is minced. Add the lemon juice and pulse several times to combine.
With the processor on, begin to drizzle the oil in so slowly that the stream turns to a dribble at times; use the oil drip hole in the top of the processor if yours has one. After 1/4 cup (60 mL) of the oil has been added, slowly pour in a tablespoon (15 mL) of the ice water. Continue slowly drizzling in the oil and slowly adding a tablespoon of ice water after every 1/4 cup (60 mL) of oil until the sauce is thickened and all of the oil has been incorporated. This takes about 7 minutes.
The sauce will be slightly thick, with some body, but still pourable. Store the toum in an airtight container in the refrigerator for several weeks.