These delectable appetisers can be adapted to a proper starter dish if you add some mixed leaves, tomatoes and vinaigrette to the plate. If you prefer to keep them as appetisers/hors d'oeuvres, you can vary their size depending on which size muffin trays you have. Either way, they are tasty and very easy to handle and eat, even if you have a Cosmopolitan or a glass of wine in the other hand!
Preheat oven to 180C. Place puff pastry rounds in a single layer on a parchment-lined baking sheet and refrigerate while mushrooms cook.
In a large skillet, heat oil over medium-high. Add shallot and cook, stirring, until soft, 3 minutes. Add mushrooms and cook, stirring, until soft and browned, 10 minutes. Season with salt and pepper. Stir in thyme and remove skillet from heat.
Lightly oil muffin cups. Divide mushroom mixture and cheese among cups, then top each with a chilled pastry round. Bake until pastry is golden brown and puffed, about 25 minutes, rotating pan halfway through.
Run a small knife around cups to loosen tartlets. Place a rimmed baking sheet or large plate over pan and invert to release tartlets. Sprinkle with more thyme. Serve warm.