Fish Pie

Name: Fish Pie
Prep time: 20 min
Cook time: 1 h 30 min
Total time: 1 h 50 min
Cuisine: European, British
Ingredients: 14 1⁄10 oz boneless pollack, haddock or cod fillet, skinned + cut into chunks; 3 5⁄10 oz cooked peeled prawns; 3 5⁄10 oz frozen baby broad beans; 1 small onion, chopped; 1 tbsp cornflour; A small handful of parsley, chopped; 9⁄10 oz unsalted butter; 7⁄10 oz plain white flour; 60 tsp whole milk; 2 6⁄10 oz Gruyère cheese, grated; 21 2⁄10 oz Maris Piper potatoes, peeled + cut into 1 cm/½ inch cubes