Maple Filling
1 1/2 cups maple sugar. 1/2 cup sweet milk. 1 tablespoon butter. Boil until it spins thread. Take from fire, beat until cold.
A three-ingredient boiled maple frosting of the fudge family. Everything depends on where you stop the boil and how long you beat it afterward.
- "Spins a thread"That is the thread stage, 230-235F on a candy thermometer. Below it the filling stays a syrup that soaks into the cake; much above it and you get maple candy you cannot spread.
- Beat until coldThis is the hinge. Cooling with constant agitation forces fine crystals and turns the syrup opaque and spreadable. Let it cool undisturbed and it sets coarse and grainy. A mixer with the paddle will shorten the work, though the time varies with the batch.
- Maple sugarGranulated or grated hard maple sugar, sold in blocks and tubs by producers. It is not the same as maple-flavoured sugar. Pure maple syrup can stand in but carries far more water, so the boil runs much longer and the yield shifts.
- Sweet milkSimply fresh whole milk, specified to distinguish it from the sour milk and buttermilk called for elsewhere in period baking. Nothing cultured belongs here.
- The panUse a heavy saucepan at least three times the volume of the ingredients. Milk sugar syrups climb and scorch readily, and scorched maple tastes burnt through the whole batch.
- If it stiffens too fastBeat in a teaspoon of hot milk or cream at a time until it drops from the spoon. Once spread it firms again as it stands.
- YieldAbout a cup and a quarter, enough to fill and thinly top one eight- or nine-inch layer cake.
Maple sugar was the working sweetener of the northern American kitchen long before cane sugar became cheap and universal, and hard cakes of it kept far better than syrup in a farmhouse pantry. Boiled fillings of this type, sugar and milk cooked to the thread and beaten cold, are the same technique as fudge and penuche, and appear across nineteenth and early twentieth century American cookbooks under a dozen names. Mrs. Mary A. Wilson wrote for Philadelphia readers in the years around the First World War, when federal food conservation campaigns pressed households to spare wheat and cane sugar, and a filling that leans entirely on maple sugar would have read as thrifty as well as good.