Preheat the oven to 220°C (200°C fan/425°F/Gas 7).
Roll out the puff pastry and divide into 12 even-sized rectangles. Spread a teaspoon of cream cheese over each one, then set aside.
Drizzle a little olive oil over the whole tray, followed by a sprinkling of salt and pepper and a scattering of fresh rosemary leaves.
Lay the mushrooms down onto the tray in 12 evenly spaced out places, I use 1 mushroom per vol au vent (cut in half if they're on the large size) and I space them out 3 rows across by 4 rows down.
Place 1 sliver of garlic on top of each mushroom and then generously grate the parmesan all over the tray. Lay the squares of puff pastry cream cheese side down onto the mushrooms.
Score the top of each vol au vent with a cross, brush with beaten egg and bake for 25 minutes or until golden. Remove from the oven and let them sit for 5 mins before flipping each one over. Test that they're loose first and you should be able to pick them up by hand and flip them right side up.
