1. Wipe the mushroom with a clean cloth dipped in cold water to which a few slices of lemon or a few drops of white vinegar has been added.
2. Cut out the stalks from the mushrooms (They can be used for cooking).
3. Soften the cheeses and beat together until smooth, then beat in the cream.
4. Put into a piping bag fitted with a star nozzle.
5. If preparing ahead, place the mushrooms, covered, and the bag with the filling, in the refrigerator until just before serving.
6. Pipe the cheese mixture into the mushrooms.
7. Top each with a nut and a basil or parsley sprig. Makes 12 to 14.