Mushroom, Onion, And Münster Tart

Directions

1. 1
   Preheat oven to 450°. Pour oil into a 12- by 17-in. rimmed baking pan and lightly oil with a paper towel. Sprinkle pan with cornmeal.
2. 2
   On a lightly floured surface, stretch dough with hands and/or roll with a rolling pin into a rectangle roughly the same size as the pan. Transfer dough to pan, stretching to fit. Fold over 1/2 in. of dough around edges to form a slightly raised rim for the tart. Prick dough all over with a fork.
3. 3
   Heat a large frying pan over high heat. When hot, add olive oil and swirl to coat. Add mushrooms and thyme; sprinkle with salt and freshly ground black pepper. Cook mushrooms, stirring, until they stop giving off liquid and start to brown. Add chopped onions, reduce heat to medium-high, and cook, stirring until onions are softened, about 4 minutes. Scatter mushrooms and onions over tart dough, then sprinkle cheese evenly on top.
4. 4
   Bake tart until cheese is melted and beginning to brown and crust is crisp and well browned, 20 to 25 minutes. Lift out of pan with a spatula, cut into roughly 2-in. squares, and serve immediately.
5. 5
   Make ahead: The tart can be made up to 2 days ahead and kept wrapped in waxed paper at room temperature. To serve, unwrap and reheat 10 minutes at 200°.
6. 6
   Note: Nutritional analysis is per hors d'oeuvre.