Add in the chopped mushrooms and cook 5 minutes. Finally, add cream and parsley and simmer until the mixture has a paste-like consistency.
Unroll puff pastry. Spread ⅓ of the paste in a strip in the center of the pastry. Lay the baked mushrooms on top in a single line. Cover with the rest of the paste.
Lift one side of the puff pastry and cover the filling. Do the same with the other one. Tuck the short ends of the puff pastry underneath. Cut the pastry diagonally with a sharp knife.