Maple Parfait

A still-frozen parfait from the era before home ice-cream machines: a cooked egg-and-syrup base lightened with whipped cream and frozen without churning. The base does the work, so cook it properly and the texture takes care of itself.

• Cook the base over water"Cook until mixture thickens" means a double boiler or a bowl over barely simmering water, stirring constantly until the mixture coats a spoon, around 170F. Over direct heat the eggs scramble and the parfait turns grainy.
• Pour the syrup slowlyThe hot syrup is being used to temper the eggs. Add it in a thin stream with the whisk moving, or you will cook lumps of egg into the base before it ever reaches the pan.
• Cool it completelyThe base must be cold, not merely warm, before the cream goes in. Warm base deflates whipped cream and the finished parfait freezes dense and icy rather than light.
• "Thick cream"This means heavy or whipping cream, 36 percent fat or better. A pint is 2 cups, which whips to roughly a quart. Half-and-half or "light cream" will not hold air.
• Maple syrupA cup of any pure maple syrup works; a darker grade gives noticeably more maple flavour in a frozen dessert, where cold mutes sweetness and aroma. Pancake syrup, which is corn syrup with flavouring, freezes harder and tastes flat.
• Salt and icePacking a sealed mould in a bucket of crushed ice layered with rock salt, about one part salt to three or four parts ice, brings the surrounding brine well below freezing. A covered loaf pan or mould in a home freezer does the same job; allow four to six hours rather than three, since still air transfers heat far more slowly than a wet salt-and-ice pack.
• No churning neededThe whipped cream supplies the air, so the mixture is not stirred while it freezes. Do not be tempted to beat it partway through; that is for ice cream, and here it only knocks out the volume.
• YieldAbout a quart and a half, serving eight. Let it stand a few minutes at room temperature before unmoulding and slicing.