To two cupfuls of cold mashed POTATOES add a half cupful of milk, a pinch of salt, a tablespoonful of butter, two tablespoonfuls of flour and two eggs beaten to a froth. Mix the whole until thoroughly light; then put into a PUDDING or vegetable dish, spread a little butter over the top and bake a golden brown. The quality depends upon very thoroughly beating the eggs before adding them, so that the potato will remain light and porous after baking, similar to sponge cake.
The Whitehouse Cookbook, by Mrs. F.L. Gillette (Year 1887)