Sponge Cake Sandwiches

An uncooked filling of three ingredients, spread between slices of sponge cake. The only technical demands are the maple sugar and the age of the cake.

• Maple sugarHard cakes or blocks of pure maple sugar were sold alongside groceries in this period; the granulated maple sugar sold today needs no crushing beyond a whirl in a food processor. One cup weighs somewhere around 5 to 6 oz. Maple sugar is drier and less hygroscopic than brown sugar, which is likely why the cream is called for to bind it.
• CrushingIf working from a solid block, break it up in a bag with a rolling pin and sieve out the coarse grains, or the filling will be gritty. The finer the sugar, the more evenly the cream is absorbed.
• Heavy creamThree tablespoons is a starting point, not a rule. Add it a spoonful at a time until the mixture just holds together as a thick paste; too much and it will soak into the cake and slump out the sides.
• Two-day-old cakeThis is the hinge. Fresh sponge tears and compresses under a stiff filling, while a day or two of drying firms the crumb enough to slice thin and spread against. Keep the cake whole and loosely covered so it stales rather than dries out at the cut face.
• SlicingThe instruction not to cut until the last moment presumably guards against the exposed crumb drying and going leathery. Thin slices, on the order of 1/4 inch, cut with a long serrated knife in a sawing motion without pressing down, suit a stiff filling.
• NutsThe recipe leaves the nut unspecified; walnuts or hickory nuts both suit maple. Toasting and cooling them before chopping gives better flavour and less oil bleeding into the filling.
• Yield and servingA cup of sugar and a cup of nuts makes a generous quantity of filling, though the recipe states no yield and no size or shape of cake. Following the recipe's own instruction, cut and assemble close to serving; the original recommends them with hot chocolate.