Preheat oven to 375 degrees. Cut out 4 heart shapes from parchment or foil, each 14 inches wide by 9 inches long. Lightly butter foil, if using. Place seasoned salmon on 1 side of parchment or foil. Heat medium skillet on medium high heat. Add butter and melt. Add mushrooms and saute until slightly golden. Add shallots, salt and pepper. Cook 2 minutes. Add chayote and wine. Cook until almost dry. Add epasote and lemon juice. Cool. Divide mixture between salmon fillets, mounding slightly. Fold second half of parchment over salmon, enclosing completely. Fold edges over to secure tightly.
Place parchment packages on baking sheet. Bake until packets are puffed and salmon is cooked through, about 10 minutes.