Pre heat oven to 220°C / 425°F / Gas Mark 7.
Cut and raw fish into small bite size pieces.
Place milk in a small pan with raw fish and poach the fish in the milk for 3minutes. The fish is cooked when it is opaque. Remove pan from heat.
Lift fish from pan with a slotted spoon and place fish on a plate along with any cooked fish you are using.
To make sauce, place other sauce ingredients in the pan. Bring to boil over a medium heat, stirring all the time with a whisk or a wooden spoon until thickened. Season. Adjust consistency with a little more milk if necessary but it should be quite a thick sauce. Gently stir in fish, herbs and seasoning to taste and set aside to cool a little.
Meanwhile cut pastry into 4 equal parts and roll out each one thinly on a lightly floured surface to make squares.
Brush the edges with milk or water. Place an equal amount of fish mix in the centre of each. Fold over one corner to diagonal corner to create a triangular parcel. Pinch edges gently together to stick.
Place on a greased baking sheet and brush each square with milk to glaze. Using a sharp knife, cut a small cross on the top of each for the steam to escape during cooking.
Bake for approx 8 minutes until the pastry is well risen and golden.
