Scotch Potatoes

A plain scalloped dish of equal parts potato and onion under a heavy white sauce. The proportions are the whole point, and the only real decisions are the thickness of the sauce and the heat of the oven.

• A quart of eachThe recipe gives the quart before the cutting instruction, so it is not clear whether the measure is taken whole or cut; either way a quart of potato is roughly 1 1/4 to 1 1/2 lb and a quart of onion about 1 lb. Equal volumes, not equal weights — the onions collapse considerably in cooking, so the finished dish reads as potato-forward.
• Hot ovenA hot oven in books of this period is usually taken as somewhere around 400–450F. Since everything in the dish is already cooked, the 25 minutes is only to set and brown the sauce.
• Thick Cream SauceThis refers back to the book's own sauce recipe. Thick white sauces of this period generally run somewhere between 3 and 4 tablespoons each of butter and flour to a cup of milk or cream. It needs to be genuinely thick, since the drained vegetables will still shed water into it in the oven.
• Boiling them togetherHalf-inch onion rounds are done in 10–12 minutes; potatoes of the same thickness need 20 or more. Boiling them together for the full half hour leaves the onion nearly a purée. Adding the onions partway through keeps the rings distinct.
• Drain hardBoth vegetables hold water in the cut faces. Let them steam dry in the colander for a few minutes before saucing, or the sauce thins and breaks at the edges of the dish.
• SeasoningOne teaspoon of salt goes into the cooking water, which mostly drains away. Season the cream sauce properly — salt and white pepper, with nutmeg if you like it — or the dish arrives flat.
• YieldServes six as a side dish. Use a shallow baking dish rather than a deep one so the sauce browns over the whole surface, and serve it in the dish as directed.