Fish pie with mashed potato topping

Name: Fish pie with mashed potato topping
Prep time: 30 min
Cook time: 2 h
Total time: 2 h 30 min
Cuisine: European, British
Ingredients: 30 g olive oil; 500 g boneless white fish fillets, cut into pieces (3-4 cm); 120 g smoked salmon, cut into strips (6 x 2 cm); 250 g cherry tomatoes (1 punnet), cut into halves; 2 pinches sea salt; 2 pinches ground black pepper; 1 brown onion, cut into halves; 1 leek (approx. 110 g), trimmed and cut into pieces; 120 g bacon, cut into pieces; 3 - 5 sprigs fresh flat-leaf parsley, leaves only; 30 g unsalted butter; 30 g plain flour; 130 g water; 1 tsp Vegetable stock paste (see Tips); 70 g sour cream or pouring (whipping) cream; 50 g Parmesan cheese, crust removed and cut into pieces (3 cm); 1000 g floury potatoes (e.g. Red Pontiac, Royal Blue), peeled and cut into pieces (2-3 cm); ½ - 1 tsp salt, to taste; 250 g full cream milk; butter, for shaving; 1 - 2 pinches ground nutmeg (optional)