Fish pie

Name: Fish pie
Prep time: 15 min
Cook time: 1 h
Total time: 1 h 15 min
Yield: 2 servings
Cuisine: British, European
Ingredients: 4 Baking potatoes; 1 sprinkle of Dry chives; 1 tsp of English mustard; 350 gr of Frozen fish pie mix; 1 handful of Grated mozzarella; 1 Leek; 25 gr of Plain flour; 500 ml of Semi skimmed milk; 50 gr of Shelled peas; 50 gr of Unsalted butter