3 tbsp chives, chopped
110g/4oz mushrooms, sliced
1 shallot, peeled and chopped
2 tbsp grain mustard
salt and freshly ground black pepper
olive oil
110ml/4fl oz fish stock
110ml/4fl oz double cream
1 egg, beaten
4 slices Emmenthal cheese
300g/10陆oz ready-to-roll puff pastry
700g/1陆lb fish, cut into chunks (salmon, cod, haddock or mixture)