| 1 | In a large heavy skillet, heat 2 tablespoons of oil over medium-high heat until hot but not smoking. |
| 2 | Add the onions and saute them until just limp, about 3 to 4 minutes. |
| 3 | Add the remaining oil, then stir in the mushrooms. |
| 4 | Adjust the heat to high and cook the mushrooms until the moisture has almost completely evaporated, 7 minutes, stirring often. |
| 5 | Remove the pan from the heat, stir in the cheese, chervil and pepper, and set the filling aside while rolling out the pastry. |
| 6 | Lightly flour a clean workspace. |
| 7 | Unfold the pastry and dust lightly with flour. |
| 8 | Using a floured rolling pin, roll the pastry into a rectangle about 12-by-18 inches. |
| 9 | Cut the rectangle into 2 long rectangles measuring 6-by-18 inches each. |
| 10 | Brush off the excess flour, and spread half of the mushroom mixture over each rectangle, leaving a 1-inch border at the uppermost edges. |
| 11 | Starting with the bottom long edge, roll up each rectangle jelly roll fashion gently pressing the top edge to seal the pastry. |
| 12 | Carefully wrap the rolls tightly in plastic wrap or foil. |
| 13 | Flatten each roll slightly by pushing gently on the sides so the spirals will be oval-shaped, and refrigerate until the pastry is firm, at least 2 hours. |
| 14 | This may be done up to 4 days ahead of time. |
| 15 | Preheat oven to 375°F, and line a cookie sheet (or 2 if you have them) with baking parchment. |
| 16 | Remove the rolls from the refrigerator as you are ready to cut them. |
| 17 | With a sharp knife, cut the rolls crosswise into 3/8-inch slices. |
| 18 | Place each oval onto the parchment, leaving 1 ?inches of space between them. |
| 19 | Transfer the pan(s) to the middle of the oven, and bake until the tops are lightly browned. |
| 20 | With a spatula, turn the spirals over and continue cooking until the second side is lightly browned and the centers are cooked through. |
| 21 | If using 2 pans, rotate the pans during baking for even baking. |
| 22 | Remove the pans, slide the swirls onto a rack to cool, and continue in the same fashion until all the swirls are baked. |
| 23 | Serve warm. |
| 24 | Note: if using your food processor to chop mushrooms, you will be far more successful if you pulse them several times to reach the desired consistency rather than let the machine run. |
| 25 | Over-processed mushrooms are often watery and will not brown |
