Milk Filling

Three lines and no context: this is a boiled milk-and-sugar filling of the kind that sets between cake layers, closer to a soft fudge than to a buttercream. The whole outcome hangs on how far the syrup is boiled and how long it is beaten.

• Filed under the wrong headingThe section marking says Vegetables, though nothing here is a vegetable dish. Whatever the reason, treat it as a cake filling.
• The measurementsTen tablespoons of milk is a scant 2/3 cup, about 150 ml. "Sweet milk" simply means fresh whole milk, as opposed to the soured or buttermilk that period recipes call for by name. With 1/2 cup sugar this is a very small batch.
• Six minutes is not the real instructionSix minutes is not much of an instruction -- boiling time depends on pan width and heat. What matters is concentration: fillings of this family are usually beaten at about the soft-ball stage, roughly 235-240F, though the recipe itself names no temperature. A thermometer is a steadier guide than the clock.
• Why you beat it coolBeating a hot saturated syrup as it cools forces the sugar into fine crystals, turning it from clear and runny to opaque and spreadable. Stop beating too early and it stays a sauce; beat too long off the heat and it seizes into a stiff crumbly mass.
• ScorchingMilk sugars catch on the bottom long before water-based syrups do. Use a heavy pan, keep the heat moderate, and stir until the sugar is dissolved.
• If it sets too hardA teaspoon of hot milk worked in during beating will loosen it. Working quickly matters more than anything else once it begins to thicken.
• YieldRoughly enough for one layer of an 8-inch cake. Double it if you want to cover the sides as well.