Preheat the oven to 220oC/Fan 200oC/Gas 7. Trim long stalks on the mushrooms then pair them up – one for the base and one place upside down on top – they want to be similar sizes.
Mix the garlic and parsley together with a little salt and plenty of black pepper, then divide the mixture between the bottom mushrooms.
Top with 2 slices of Brie, the roasted pepper, and then the upside down mushroom – tuck the cheese and peppers neatly inside the two mushrooms.
Cut the pastry block into 4, then on a lightly floured surface roll out each piece to a rough circle about 17cm wide. Place a mushroom parcel in the centre, brush the pastry edges with a little egg, then gather up around the mushrooms and pinching to seal. Repeat to make four parcels.
Arrange the mushrooms on a baking parchment lined tray. Make a little steam hole on the top, then brush with more beaten egg. Bake for 25-30 minutes or until the parcels are golden. Serve hot with vegetables.