Onion Gruyere Tart

Preparation

1. Step 1

   Cut onions into slices about ¼ inch thick. Chop coarsely.

2. Step 2

   Heat butter and oil in heavy skillet. Add onions and cook, covered, over medium heat about 10 minutes, or until onions are limp and begin to render liquid. Add pinch of sugar.

3. Step 3

   Uncover onions and cook over medium-high heat 30 to 45 minutes. Stir frequently with a wooden spoon or spatula to scrape up brownings in pan. The onions should be a deep brown and reduced to a small mass. They must be watched carefully and stirred to prevent scorching and to ensure even browning.

4. Step 4

   Transfer onions to a bowl. Add wine to skillet and boil, scraping up pan brownings, until liquid is reduced to a thick glaze. Add glaze to onions, along with salt, nutmeg, cream and egg. Adjust seasoning. (Dish may be prepared to this point a day in advance and refrigerated.)

5. Step 5

   Preheat oven to 375 degrees.

6. Step 6

   Grate cheese and distribute half of it on bottom of chilled pastry shell in pastry tin. Distribute onion mixture evenly over cheese; top with remaining cheese.

7. Step 7

   Bake 40 to 45 minutes. If top browns too much, reduce heat slightly toward the end. Serve as a first course, warm or at room temperature. Tart can be made a few hours ahead, but do not refrigerate.