2 teaspoons chopped herbs, such as tarragon, chervil and chives, plus extra to garnish (optional)
salt and pepper
Line a baking sheet with baking paper. Arrange the vol-au-vent cases on it and bake in a preheated oven, 220˚C (425˚F), Gas Mark 7, for 10–12 minutes, or according to the packet instructions, until crisp and golden.
Meanwhile, melt the butter in a frying pan and cook the onion and garlic over a medium heat for 6–7 minutes, stirring occasionally, until softened and golden. Add the mushrooms and fry for a further 3–4 minutes, until softened.
Stir the mascarpone and herbs into the pan, add a pinch of salt and pepper, then remove from the heat.
Spoon the filling into the pastry cases and serve warm, garnished with freshly snipped chives, if desired.