1 sheet frozen puff pastry
1 1/4 pound mixed wild mushrooms (such as 3 1/2 ounces each oyster,hedgehog, white shimeji & yellow chanterelles) plus 8 ounces criminis)
1 tablespoon each unsalted butter and olive oil to sauté each 3 1/2 ounces of mushrooms, double to sauté 8 ounces.
3 tablespoons mixed fresh herbs, such as thyme, tarragon, chervil, parsley and chives
1 extra large egg yolk
3/4 cup (6 oz) crème fraîche
2 1/2 ounces Gruyère or Emmentaler cheese, shredded