Frozen Custard

A French-style ice cream base — egg yolk custard thickened with a token amount of starch — written for a hand-cranked freezer packed with ice and rock salt. The instructions stop short at two points that matter, and the batch is larger than most home machines will take.

• Cook the eggs, don't just stir them inAs written the beaten eggs go into the hot milk and the mixture goes straight to the freezer. Return the pan to low heat after adding them and stir until the custard coats a spoon, around 170–175F; below that the eggs neither thicken reliably nor reach a temperature that makes them safe to eat cold.
• Scald means 180FScald means roughly 180F -- Bring the milk to the point where it steams and shivers at the edges, not a rolling boil. "Rich milk" in this period generally meant unskimmed milk, and may have implied some cream in it; whole milk is a reasonable modern reading, and for a richer result substitute a quart of cream for one of the quarts of milk.
• Twenty minutes needs a double boilerMilk and starch held twenty minutes over direct heat will scorch and take on a cooked flavour. Use a double boiler or the lowest possible flame with frequent stirring.
• The cornstarch quantity is very smallThree-quarters of a tablespoon in two quarts of milk is barely a thickener; it functions here as insurance against the eggs curdling and against iciness in the frozen custard. Read it as written rather than scaling it up — the eggs do the real work.
• Flavouring"1 teaspoonful lemon and vanilla extract" is ambiguous; it most likely means a teaspoon of each, though a single teaspoon of the two combined is a possible reading. Add them after the custard is off the heat, since alcohol-based extracts lose aroma in a hot pan.
• Chill before churningThe custard must go into the freezer cold — refrigerate to 40F or below, ideally overnight. Warm base churns slowly, overruns with air, and freezes coarse.
• Batch sizeThis makes roughly two and a half quarts of base, more than most domestic ice cream machines hold. Churn in two batches, or halve the recipe. Expect twelve to sixteen servings from the full quantity.
• Freezing without a machineAn ice-and-salt bucket freezer is packed in layers of crushed ice and rock salt; published ratios vary, commonly somewhere between one part salt to three parts ice and one part salt to eight. Lacking either, freeze in a shallow pan and beat the mixture thoroughly every thirty minutes until set, or the texture will be granular.