Preheat oven to 450 degrees. Using a fork, prick puff pastry disks all over, transfer to baking sheet and chill again, if at all softened. Bake in center of oven until pastry is golden brown and crisp, about 10 minutes. Cool disks completely on wire racks.
Heat oil in a skillet over medium-low heat and sweat sliced mushrooms until tender. Add chopped mushrooms, shallots and garlic and moisten with stock. Cook until mushrooms have absorbed most of stock. Stir in nuts. Generously season to taste with salt and pepper. To assemble, spread half of mushroom filling on a pastry layer, top with pastry, and repeat, ending with plain pastry on top. Stir truffle flavoring into mayonnaise and spread a thin layer over top. Sprinkle with chopped herbs. Serve immediately.
Yield: 2 servings