Scalloped Sweetbreads with Mushrooms

A one-line variation that assumes you already have the preceding preparation in hand: sweetbreads parboiled, trimmed and bound in a cream sauce, then baked in shells under crumbs. The notes below cover what the shorthand leaves out.

• What the base preparation is"Prepare as in the foregoing recipe" is not reproduced here, but for scalloped sweetbreads it would almost certainly mean blanched, trimmed sweetbreads broken into pieces and folded into a thick white or cream sauce. Without that step you have nothing to scallop; make the sauce stiff enough to hold a spoon mark, since the mushrooms will loosen it.
• Sweetbreads need soaking and blanching firstSoak in several changes of cold water for an hour or two to draw the blood, then simmer 15-20 minutes in acidulated water, cool, and strip the membrane and any tubes. Skipping this leaves them grey, soft and faintly livery. They are thymus and pancreas from veal or lamb; ask a butcher, as supermarkets rarely stock them.
• Stew the mushrooms before they go inRaw mushrooms shed a great deal of water into a bound sauce. Cook the chopped mushrooms in butter until the liquid has come out and evaporated, which is what "stewed" means here, then add them.
• "An equal amount"The original does not say whether by weight or by volume; equal volume, measured after chopping, is the easiest reading. That is a generous proportion; half as much still reads clearly if you want the sweetbreads to lead.
• Scallop-dish or shellsA shallow gratin dish, or individual ovenproof shells (roughly half to three-quarters of a cup each). Fill them level rather than heaped so the crumbs brown evenly.
• Buttered crumbsDry crumbs tossed with melted butter, roughly a tablespoon of butter to a half cup of crumbs, spread thinly. Panko works but browns faster.
• "Brown as before"The original gives no temperature. A hot oven, in modern terms around 400-425F, for 15-20 minutes, until the filling bubbles at the edge and the crumbs are deep gold, works. If the filling was already hot when it went into the dishes, a minute or two under the broiler is enough.
• YieldA pair of veal sweetbreads with equal mushrooms fills four to six individual shells, enough for a light first course or a luncheon dish.