Vassar Fudge

A plain chocolate fudge of the kind that circulated in handwritten copies among college women. The recipe assumes you know what "thick" looks like; the notes below fill in what the original leaves to experience.

• The hinge: cool before you beatFudge sets smooth only if the sugar crystallizes small. Beating a boiling-hot syrup gives a grainy result, so let the pan stand off the heat until it has dropped to about 110F (the bottom is merely warm to the hand) before stirring hard. Stop when the gloss dulls and it stiffens, then pour at once.
• Squares of chocolateA square of unsweetened baking chocolate is 1 oz, so this needs 2 oz total. Unsweetened is essential; the sugar in the recipe is calculated against it.
• Butter the size of an eggRoughly 2 oz, or 4 tablespoons. Nineteenth-century recipes often gave butter by comparison with familiar objects rather than by weight.
• Four minutes is not a reliable measureBoiling time depends on the pan, the burner and the altitude. What matters is the soft-ball stage, 234-238F on a candy thermometer, or a drop that flattens into a soft ball in cold water.
• When to add the vanillaThe original lists it among the ingredients melted together, but vanilla's aroma boils off. Add about a teaspoon after the pan comes off the heat, before or as you start to beat.
• Don't stir while it boilsStir only until the sugar dissolves, then leave it alone. Agitation and stray crystals on the pan sides both seed coarse grain; a damp brush around the inside of the pan takes care of the latter.
• Pan and yieldUse a saucepan several times the volume of the mixture, as milk and sugar climb. It makes upwards of a pound, enough for a buttered 8 x 4 inch loaf pan or a small square tin, cut into 16 pieces.