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Pistachio Biscuit
Have ready two basins and put the whites of a dozen eggs in one and the yolks in the other; mix with the yolks a pound of sugar, four ounces of blanched pistachios powdered to a pulp, adding a little white of egg to prevent them from oiling. The whites should then be whisked to a froth and turned into the basin with the yolks and pistachios, sifting in about six ounces of dried flour and the rasped rinds of a couple of lemons. Stir gently, and pour the mixture into moulds or paper cases, sprinkle well with caster-sugar, place in a moderate oven and bake. When done, allow them to get cold and they are ready for use.
This is a biscuit in the old French sense — a whisked sponge batter leavened only by egg, with no butter and no chemical raising. Everything depends on how much air survives the folding.
- Fold, do not stir"Stir gently" is the language of the period, but the whites are the only leavening in the batter. Fold the whites and the sifted flour in alternately with a large spoon or spatula, stopping the moment no dry streaks remain.
- Moderate ovenRoughly 350F. Small paper cases will take about 15-20 minutes, a larger mould 30-40; the recipe gives no time at all, so judge by eye. Bake until the tops spring back and a skewer comes out clean.
- Weights, in cupsA pound of sugar is about 2 1/4 cups; six ounces of flour is roughly 1 1/3 cups; four ounces of pistachios is about a cup shelled. Weighing is much more reliable here, since the batter has no margin for error.
- "Dried flour"Flour was warmed in a low oven or by the fire to drive off damp before sifting. Modern bagged flour needs only sifting.
- The pistachio pasteGrinding nuts to a pulp releases their oil, which weighs the batter down; the splash of egg white is there to keep the paste emulsified. Work them in a food processor with a spoonful of the whites, in short pulses, and stop before it turns to butter.
- Rasped rindA rasp meant a coarse grater then; use a microplane and take only the yellow zest of the two lemons. Any white pith turns bitter in a plain sponge like this.
- Caster-sugar on topSuperfine sugar, sprinkled before baking. It draws moisture from the surface and sets into the thin crisp shell you find on ladyfingers — do not skip it, and do not substitute granulated, which sits in gritty beads.
- Moulds and paper casesButter and flour metal moulds well; the batter is lean and clings. Paper cases can sit on a sheet pan without support if the batter is properly aerated.
- YieldTwelve eggs and a pound of sugar make a very large batch — roughly three to four dozen small cakes, or two 9-inch sponges. Halving works cleanly.
Biscuit here is the French pastry term -- the same family as biscuit de Savoie and the ladyfinger -- meaning a foam of separately beaten yolks and whites bound with a little flour, and it has nothing to do with the American soda biscuit. The instructions assume the reader already knows what a whisked biscuit batter should look like and how long to leave it in. Pistachios were a comparatively costly imported nut in this period, valued for the green they lend a pale crumb as well as for flavour. The trick of grinding nuts with a little egg white to keep them from oiling appears in nineteenth-century pastry manuals and remains sound practice.