* Other wild or cultivated mushrooms may be substituted ** See recipes for Puff Pastry, Bordelaise Sauce, and Veal Stock.
Roll out your puff pastry to large rectangle, 1/8-inch thick. Use a 5-inch oval or 4-inch round cutter to cut out 4 pieces of pastry. Place them on a baking sheet. Stir together the egg yolk and water and lightly brush the pastry with this egg wash. Chill pastry for 30 minutes.
Preheat oven to 400 F. Bake feuilletes for 20 minutes, then lower the temperature to 350 F and continue to bake until they''ve turned golden brown (about 5 to 10 minutes longer.) Cool them on a rack.
In a saucepan, heat 3 tablespoons of butter over medium-high heat and add the shallot, stirring until wilted (about 2 minutes.) Add the chanterelles and cepes and stir until quite dry (6 to 8 minutes.) Add snails and toss well.
Add 3 tablespoons of Cognac, light the alcohol carefully with a long handled match, and cook 1 to 2 minutes. Transfer this mixture to a sieve placed over a bowl and return the pan to heat. Add red wine and reduce by half, scraping up any browned bits in the pan (about 4 minutes.)
Add Bordelaise sauce, or veal stock and reduce until thickened enough to coat a spoon lightly, 3 to 5 minutes. Remove the pan from the heat, swirl in the remaining butter a little at a time, and adjust seasonings to taste with salt and pepper and a few drops of Cognac.
For Garnish: Slice the tops off of the feuilletes and scoop out insides. Return feuillettes and their lids to the oven briefly to reheat. In a small saucepan, combine the mushrooms, water, lemon juice and 1 tablespoon of butter. Bring to a boil over medium-high heat; cover and cook, shaking the pan occasionally, until just tender (about 4 minutes.) Remove the mushrooms; drain them and cut them into thick slices.
To Assemble: Add the snail-mushroom mixture to your sauce and bring it all to a simmer. Place heated pastry shells on 4 heated plates and fill with snail mixture. Garnish with mushroom slices by overlapping them along 1 edge of each shell. Spoon any remaining sauce over, replace lids at a slight angle, and serve immediately.