Cake Filling

A two-ingredient boiled filling that relies entirely on reduction, with nuts stirred in at the end. The whole recipe hinges on how far you take the milk.

• What "until it thickens" meansThere is no flour, cornstarch or egg here, so the only thickening is evaporation — you are making a loose milk caramel. Expect a good stretch of steady simmering in a wide pan, likely a quarter of an hour or more, before one cup of milk reduces to a spreadable mass, and stir often once it starts to darken at the edges.
• Test by cooling, not by lookingHot, it will always seem too thin. Drop a little on a cold saucer; when it sets to the thickness of thick jam it is done. The saucer is the surer test here: the receipt gives no temperature, and a thermometer reading in the soft-ball range is at best a rough guide.
• Scorching is the real riskReducing milk and sugar with nothing to protect the bottom of the pan invites burning. Use a heavy-based saucepan, keep the heat moderate rather than high, and scrape the corners with a flat-edged spoon or spatula.
• "A small piece of butter"Read this as roughly one tablespoon. Add it off the heat with the nuts; it smooths the texture and keeps the filling from setting hard.
• Hickory nutsShagbark hickory was a gathered nut rather than a shop item across much of the rural Northeast, and cracking them is slow work. Pecans are the closest relative in flavour and texture and substitute cup for cup; walnuts work but are more tannic.
• MilkWhole milk is assumed. Skim milk will take much longer and taste thin; a mix of whole milk and a little cream reduces faster and richer, which is closer to the farm milk the receipt expects.
• Yield and useEnough for one layer of an 8- or 9-inch cake, or the top of a small loaf. Spread it while still warm and pliable — once fully cold it stiffens and tears the crumb.