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Lemon Rock Biscuits
Rub the yellow rind of two fresh lemons upon a quarter of a pound of loaf sugar. Powder it, and mix it gradually with the white of an egg whisked to a firm froth; beat thoroughly. Butter some writing-paper, place it on an oven tin, drop the mixture upon it from the end of a spoon in rock-like shape, and place it in a cool oven to dry. Time, half an hour to beat the sugar and egg. Probable cost, 5d.
This is a lemon meringue drop under an older name: sugar, egg white and citrus oil, dried rather than baked. Two details carry the whole thing, the rubbing of the rind and the very low oven.
- Rub the rind, do not zest itDragging a whole lemon across a hard sugar lump strips the oil-bearing surface only, leaving the bitter white pith behind, and the sugar absorbs the oil. Modern loaf sugar is hard to find; a large sugar cube pressed against the fruit works, or rub finely grated zest into caster sugar with your fingertips until the sugar is damp and fragrant.
- Loaf sugar and "powder it"Loaf sugar was a cone of hard refined sugar, broken and ground as needed. A quarter of a pound is 4 oz, roughly half a cup. After rubbing, grind it fine in a mortar or blitz briefly in a spice grinder; coarse grains will weep in the meringue.
- A cool ovenThe book gives no temperature; a cool oven is usually reckoned at somewhere around 200-250F (95-120C), with the door propped slightly ajar if your oven runs hot. The aim is to dry the biscuits pale, not to colour them, and too much heat will colour them and leave them chewy.
- The half hour is beating time, not baking timeThe recipe's 'time' refers only to working the sugar into the froth by hand; it gives no drying time. Expect an hour or more in the low oven, and they can be left to finish in the oven once it is switched off. With a stand mixer, five to eight minutes on medium-high gives the stiff, glossy mass the original wanted.
- Add the sugar graduallyWhisk the white to firm peaks first, then rain the lemon sugar in a spoonful at a time. Dumping it in at once collapses the foam and the mixture will spread flat rather than holding its rocky shape.
- Buttered writing-paperSubstitute baking parchment, unbuttered. Writing paper was the smooth, sized stationery of the day, greased so the sugar would release; parchment does the same job without the fat, which can slacken meringue where it touches.
- Ratio and yieldOne white to 4 oz sugar is a heavy proportion of sugar by modern meringue standards. It should give roughly fifteen to twenty small rocks, depending on the spoon. They keep a week or two in an airtight tin and go sticky quickly in a humid kitchen.
- Probable cost5d is five old pence, pre-decimal — a shorthand Cassell's uses throughout to let a housekeeper price a dish before committing to it.
Rubbing a lemon on a sugar lump to capture the oil is a long-standing trick in the English confectioner's book, and it survives in the oleo-saccharum that bartenders still make for punch; the peel's oil is far more aromatic than the juice and dissolves into the sugar rather than wetting it. "Rock" biscuits are often said to take their name from the deliberately rough, craggy shape dropped from a spoon, distinguishing them from the smooth piped or moulded meringues of the pastrycook, and similar recipes appear in Victorian household manuals as rock cakes, rock buns and lemon rocks.