Pistachio Dessert

This is a still-frozen semifreddo: an Italian meringue folded into whipped cream, with no churning. The hinge is the sugar syrup — it must be hot enough to cook the whites into a stable meringue, and it must go into the whites in a thin stream while they are beating.

• "Until it threads"Thread stage is about 230F on a candy thermometer — the syrup falls from the spoon in a fine thread rather than dropping. Below that the meringue will slump and the dessert will freeze grainy.
• Pouring techniqueThe whites need to be beating continuously while the syrup goes in, in a slow stream down the side of the bowl. Poured onto the beater or dumped in at once, the syrup sets into candy shards.
• Raw-egg noteHot syrup at thread stage heats the whites but does not reliably pasteurize them. If serving anyone pregnant, elderly, very young or immune-compromised, use pasteurized egg whites.
• Cream"Cream, whipped" here most likely means heavy or whipping cream measured before whipping - 2 cups liquid gives roughly 4 cups whipped. Whip only to soft peaks; over-whipped cream turns buttery once folded.
• Pistachio flavoringBottled "pistachio" flavoring of the period was typically almond-based. Modern pistachio extracts vary wildly, so add a few drops, taste, and stop early. Real flavor comes better from the nuts themselves.
• The nutsUse unsalted shelled pistachios, chopped fairly fine. Salted cocktail nuts will read as savory against the sugar, and coarse pieces freeze hard enough to be unpleasant.
• FreezingFive hours in an ice compartment of the period is not five hours in a modern freezer at 0F. Freeze in a shallow metal pan or loaf tin, covered, for at least 5 hours or overnight; no stirring is needed because the meringue and cream keep it soft.
• ServingSix portions from this volume are generous. Let the pan stand 10 minutes at room temperature before scooping, and it will slice cleanly.