Cook the broccoli in lightly salted boiling water for about 2 minutes or until the florets are just beginning to soften.
Meanwhile, heat the oil in a large frying pan and cook the mushrooms over a medium heat, stirring occasionally, for about 5 minutes. Stir in the Gorgonzola, mascarpone and crème fraîche. Add the drained broccoli florets and the chives, season and tip into 4 individual ovenproof dishes or 1 large rectangular ovenproof dish.
Lay the pastry over the filling, pressing it to the sides of the dish to seal. Brush the top with beaten egg and cut two slits. Cook in a preheated oven, 220°C (425°F), Gas Mark 7, for about 25 minutes until the pastry is crisp and golden. Serve immediately.