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Rock or Candy
Put a pound of loaf sugar into a saucepan with a tea-cupful of water, and stir it until it is dissolved, add a spoonful of vinegar to clear it, and carefully remove the scum. Have ready a shallow tin rubbed over with butter. When the sugar is boiled sufficiently, stir into it sliced almonds, chopped cocoa-nut, or Brazil nuts shelled and cut in slices, and pour it into the tin to the thickness of half or a quarter of an inch. If preferred, the nuts, etc., may be left out, and the rock may be simply marked across with a knife when it is almost cold. In order to ascertain when the sugar is done enough, dip a spoon into it, and raise it. If the threads thus formed snap like glass, it is ready.
A plain boiled-sugar candy that depends entirely on reading the syrup correctly. The thread test described at the end is the whole recipe; everything before it is preparation.
- The hinge: the snap testThreads that "snap like glass" mean hard crack, 300-310F (149-154C) on a sugar thermometer. Below that the slab stays tacky and bends; much above it and the sugar takes on a scorched, bitter caramel note.
- Loaf sugarLoaf sugar was refined cane sugar broken from a cone. Ordinary granulated white sugar is the direct substitute, one pound, about 2¼ cups.
- A tea-cupful of waterThe measure was not standardised; period usage runs from about a quarter-pint (5 fl oz) to roughly 6 fl oz, so ⅔ to ¾ cup. Slightly more water only lengthens the boil, so err generous rather than short.
- The spoonful of vinegarThe acid inverts a little of the sucrose and discourages graining; the phrase "to clear it," followed here by skimming, more likely refers to clarifying the syrup. A teaspoon of white vinegar or an equal amount of lemon juice does the job; more than that will be tasted.
- Stop stirring once it boilsStir only until the sugar dissolves. After that, leave the pan alone and wash any crystals from the sides with a wet brush, or the batch can seize into an opaque grainy mass.
- Cocoa-nut and almonds"Cocoa-nut" is coconut, often bought whole and grated at home in this period, though desiccated coconut was also sold; unsweetened desiccated or fresh-grated coconut both work. Warm the nuts first, as cold additions drop the syrup temperature and can set it prematurely.
- The tinA shallow buttered tin: an 8-inch square gives roughly the quarter-inch slab the recipe allows; for a full half-inch you want something smaller. Butter it well and have it standing ready before you start; the syrup sets fast.
- Marking and breakingScore with an oiled knife while the sheet is still warm and pliable at the edges, then snap along the lines once cold. Left too long it will only shatter at random.
- Yield and keepingA pound of sugar gives roughly a pound of candy, enough to fill a medium tin. Sugar at this stage is hygroscopic; wrap the pieces or hold them in an airtight jar or they will turn sticky within a day in a humid kitchen.
This is really a lesson in sugar boiling: every confection from fondant to toffee is the same syrup stopped at a different stage, and before household thermometers were common the cook learned those stages by hand, from the thread and the ball to the crack. "Rock" in nineteenth-century British usage covered hard boiled sugar in slabs or sticks, the same family as the lettered seaside rock sold at Victorian resorts, and it was a domestic economy as much as a treat, since a pound of sugar and a handful of nuts made a large tinful for very little. The nut versions belong to a wider European tradition of sugar-and-almond brittles; the vinegar, an acid to keep the syrup from graining, works on the same principle as the cream of tartar in modern recipes, while glucose and corn syrup achieve a similar result by a different route.