Cranberry Frappe

A two-ingredient fruit ice, thickened only by its own pectin and sugar. The whole trick is in the final words: freeze to a mush, not to a solid block.

• Freeze to a mushA frappe is deliberately under-frozen "snow," softer than a sorbet. In a churn, stop while it is still slushy and will slump off a spoon; without a churn, freeze in a shallow metal pan and rake it thoroughly with a fork every 30 minutes for 3 to 4 hours.
• A quart of cranberriesBerries were sold by dry measure. A dry quart of cranberries runs to roughly 1 lb, or about a cup more than a standard 12 oz bag; one bag alone works with a small reduction in water.
• Force through a sievePress hard with the back of a ladle through a medium sieve or use a food mill. This is what removes skins and seeds and leaves the puree smooth; a blender alone will not, and the skins will read as grit once frozen.
• Sugar is structuralTwo cups against a pint of water is not only for sweetness; it keeps the mixture from freezing into an unspoonable brick. Cutting the sugar much below 1 1/2 cups gives a hard, icy result.
• Dissolve while hotStir the sugar into the puree while it is still hot from the pan, so no undissolved grains remain.
• LemonsTwo lemons yield roughly 1/4 to 1/3 cup of juice; add half, taste the cooled mixture, then add the rest to suit the tartness of the berries.
• Chill before freezing"Cool" means thoroughly cold, refrigerator-cold. A warm mixture put to freeze forms coarse crystals and takes far longer to reach mush stage.
• Yield and servingSomething over a quart, or six to eight small servings. Serve at once in stemmed glasses; a frappe held in the freezer sets solid and needs to be broken up with a fork again before it goes to the table.