MAKES ABOUT 4 CUPS
1 head garlic
¾ cup lemon juice (from 3 lemons) 1 ½ teaspoons kosher salt
2 generous cups tehina
½ teaspoon ground cumin
Break up the head of garlic with your hands, letting the unpeeled cloves fall into a blender. Add the lemon juice and 1/2 teaspoon of the salt. Blend on high for a few seconds until you have a coarse puree. Let the mixture stand for 10 minutes to let the garlic mellow.
Pour the mixture through a fine-mesh strainer set over a large mixing bowl, pressing on the solids to extract as much liquid as possible. Dis-card the solids. Add the tehina to the strained lemon juice in the bowl, along with the cumin and 1 teaspoon of the salt.
Whisk the mixture together until smooth (or use a food processor), adding ice water, a few tablespoons at a time, to thin it out. The sauce will lighten in color as you whisk. When the tehina seizes up or tightens, keep adding ice water, bit by bit (about 1 1/2 cups in total), whisking energetically until you have a perfectly smooth, creamy, thick sauce.
Taste and add up to 1 1/2 teaspoons more salt and cumin if you like. If you’re not using the sauce immediately, whisk in a few tablespoons of ice water to loosen it before refrigerating. The tehina sauce will keep a week refrigerated, or it can be frozen for up to a month.