MAKES ABOUT 1¾ QUARTS/1.6 L
The Spanish tradition of drinking ices dates back to the Moorish rule of the country, using snow collected in the Sierra Nevada, the stunning range of mountains southwest of Granada. Although you can find a (limited) array of granizado flavors today, the two classics—lemon and coffee—remain the most popular.
Generally, when prepared at home, the liquid is never quite allowed to freeze and is shaken or stirred from time to time until slushy. It can be done using either a bowl or plastic bottles. (I give directions for both.) Another method that also works is to freeze it completely, and then thaw in the refrigerator, shaking and breaking up with a spoon once it is nearly slush.
1. Scrub the lemons. If waxed, dunk the lemons in boiling water and firmly wipe off the wax. Zest the lemons into a large bowl, grating only the yellow part. (The white pith is bitter.) Halve the lemons crosswise and juice them into the bowl. Drop in the lemon peels. Add 6 cups/1.4 L water. Let sit for 30 to 40 minutes.
2. Pour the liquid through a fine-mesh strainer into a large bowl. Press the lemons to get all of the liquid from them, straining that liquid, too. Stir in the sugar until completely dissolved.
3. To freeze using a bowl: Pour the liquid into a large glass or plastic bowl. Cover tightly. Place in the freezer. When it begins to freeze, stir with a fork or wire whisk. Repeat two or three times, never letting it completely freeze, until slushy, at least a couple of hours.
To freeze using plastic bottles: Place a funnel over a clean 2-quart/2-L plastic or glass bottle (or two smaller ones) and pour in the liquid. Close tightly. Place in the freezer. When it begins to freeze, shake. Repeat two or three times, never letting it completely freeze, until slushy, at least a couple of hours.
4. Ladle or pour into glasses. Garnish with mint leaves and serve with straws.