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Rock Sugar, Coloured
Take a pint of clarified sugar and boil it in a copper or earthenware pan over a clear fire till it reaches the degree of crackled. Remove it from the fire, and mix well into it a table-spoonful of icing, stirring briskly all the time with your skimmer. If no icing is at hand, mix some sifted loaf sugar with the white of an egg till it is quite thick, put in a table-spoonful, and that will answer as well. If the rock is wanted coloured, mix with the icing any of the colouring used for confectionery before you put it to the sugar. When the sugar and icing are well mixed, put the mixture into a papered sieve to cool, and when quite cold break into pieces.
This is French sucre rocher — sugar boiled hard, then deliberately grained with a little royal icing so it froths up into a porous, rock-like mass used for decorating set pieces. The instructions assume a confectioner's vocabulary that has largely dropped out of use.
- The hinge: stir just enoughAdding the icing to sugar at the crack stage makes it seize and foam up the pan; that aeration is the point of the recipe. The recipe says to mix well and stir briskly; the usual advice is to work only until the mass is uniformly puffed and then get it out of the pan, over-working being said to collapse the froth.
- "Crackled"The crack stages of sugar boiling: petit cassé around 285F and grand cassé around 300-310F. For rock, work at the upper end, about 300F on a sugar thermometer. Below that the sugar retains too much moisture and the mass stays sticky.
- Clarified sugarA strong sugar syrup boiled up with egg white and skimmed to remove the scum — a step made necessary by unrefined nineteenth-century sugar. Modern granulated sugar needs no clarifying; a pint of syrup of this kind represents somewhat over a pound of sugar dissolved in water, boiled and skimmed once.
- IcingNot powdered sugar in the modern American sense but royal icing — confectioners' sugar beaten stiff with egg white, exactly as the fallback instruction describes. "Loaf sugar" is refined sugar broken from the cone, so sifted loaf sugar is icing sugar.
- The panUntinned copper was the confectioner's choice because it heats evenly and takes the sustained high temperature. Any heavy stainless or unlined copper pan works; avoid nonstick, and disregard the earthenware option on a modern burner.
- ColouringVictorian confectionery colours included mineral pigments that no one would now put in food. Use modern food colouring, and choose a concentrated gel or paste rather than a liquid — extra water thins the icing and weakens the graining.
- CoolingA "papered sieve" is a coarse sieve or wire rack lined with parchment, which lets air reach the mass from beneath so it sets dry rather than sweating. A parchment-lined cooling rack does the same. Leave it fully cold, an hour or more, before breaking.
- Yield and keepingKeeping -- Store airtight with a desiccant if you have one; in humid air it goes tacky within a day or two.
Coloured rock sugar belongs to the decorative side of the profession rather than the dessert course: confectioners broke it into glittering shards to build the grottoes, cliffs and rockwork bases of a pièce montée, the architectural centrepiece that crowned a formal Victorian table. Its place in Cassell's is telling — sugar boiling was taught as a graded scale of temperatures, from thread through ball to crack and caramel, each judged by hand and eye before thermometers were common in domestic kitchens, and a cook who knew the degrees could produce syrups, candies, spun sugar and rockwork from one set of skills. The trick of graining hot sugar with icing to make it swell is generally traced to French confectionery practice, from which English kitchens took most of their sugar-work terminology; "crackled" here is often taken as an English rendering of cassé.