Make a rich pie-dough. Line a buttered pie-dish with the dough; then slice three onions very thin and let cook in hot butter until tender; add a pinch of salt. Fill the pie with the onions, cover the top with cream and let bake in a moderate oven until done. Serve hot or cold.
A single-crust onion tart with almost nothing in it but sweated onions and cream. The instructions leave the quantities of dough and cream to the cook, so a few decisions have to be made before you start.
- Moderate ovenRead that as 350F (175C). At that heat a 9-inch tart takes roughly 35 to 45 minutes, until the cream is bubbling and lightly browned at the edges and the pastry underneath is set.
- How much dough"A rich pie-dough" here means a short, butter-heavy crust for a single 9-inch shell — about 1 1/4 cups flour to 8 tablespoons butter. There is no top crust; the cream is the lid.
- The hinge: cook the onions gentlyThree onions sliced thin should stew in butter over low heat until soft and translucent, 15 to 20 minutes, without taking colour. Browning them turns the filling sweet and jammy, which is a different tart altogether.
- How much creamThe original gives no measure. For a 9-inch shell, 3/4 to 1 cup of heavy cream will just cover the onions; enough to coat, not to float them.
- It will not set like a custardWith no eggs, the cream thickens by reduction rather than coagulating. Expect a soft, saucy filling that firms as it cools, which may be part of why the recipe allows for serving it cold as well as hot.
- Soggy baseWet onions and cream on raw pastry are a bad combination. Blind-bake the shell 15 minutes at 400F, then drop to 350F once filled.
- SeasoningA pinch of salt is thin for three onions and a cup of cream. Season the onions properly as they cook, and a grating of nutmeg or a little black pepper is well within the tradition.
- YieldSix modest slices as a first course or lunch dish, four as a main with a salad.
Onion tarts run in a broad band across Switzerland, Alsace and southern Germany, where they are variously Zibelechueche, Zwiebelkuchen or tarte a l'oignon — pastry, sweated onions, dairy, and often bacon or caraway, which this version omits. In Bern the dish is associated with the Zibelemarit, the late-November onion market. Its appearance in a book of dishes "of all nations" is characteristic of the genre — the entries run one dish per country per day, each pared to the barest outline, more a sketch of a national idea than a working formula. Many Swiss and Alsatian versions bind the filling with egg; this one does not.