In a bowl, whisk the softened goat cheese with the cream (if using) and the beaten egg until smooth and fluffy. Stir in the parsley and a pinch of salt until well combined.
Assemble: Spoon a generous layer of mushroom mixture into each pastry round or tartlet shell. Top with a dollop of the herbed goat cheese, then give a light swirl with the back of a spoon to blend the flavors a little.
Bake for 12–15 minutes, or until the pastry is golden and crisp and the cheese is just set. If the edges brown too quickly, cover loosely with foil and bake until the centers are just firm.
Let cool for 5 minutes on a rack. Finish with a few extra parsley leaves and a light pinch of flaky sea salt, if desired.