This recipe can also be prepared in a 9-inch deep-dish pie plate.
- To make Potatoes: Put potatoes in pot, and cover with water. Bring to a boil, reduce heat to medium-low, and simmer 30 minutes, or until tender. Drain. Warm cream and butter in pot; add potatoes, and mash until smooth. Stir in Parmesan and chives, and season with salt and pepper, if desired. Cool.
- To make Filling: Heat 1 Tbs. oil in skillet over medium heat. Add onions, and cook 20 minutes, or until golden.
- Preheat oven to 375°F. Coat baking sheet with cooking spray. Set portobellos gill-side up on baking sheet, and drizzle with 1 Tbs. oil. Roast 25 minutes, or until tender. Cool, then slice thin.
- Toss wild mushrooms with remaining 3 Tbs. oil and garlic on separate baking sheet; season with salt and pepper, if desired. Roast 20 minutes, or until tender. Cool, chop, and toss with Asiago, herbs, and onions.
- Coat baking sheet and inside of 8 3-inch baking rings or 9-inch pie dish with cooking spray. Layer portobello slices on bottom of each ring. (Add any leftover portobellos to mushroom mixture.) Use half of wild mushroom mixture to create second layer. Use one-third of Potatoes to create third layer, then add remaining mushroom mixture. Top with remaining Potatoes, shaping each into dome. Sprinkle each pie with pinch of Parmesan. Bake 40 minutes, or until golden. Let cool in rings 5 minutes. Use metal spatula to transfer pies (in rings) to plates. Run paring knife around inside of rings to loosen; lift off rings.