Gluten-Free Fish Pie with Mashed Potato Topping

• 900 g Yukon Gold potato
• 2 tsp Fine sea salt
• 70 g Butter
• 550 ml Whole milk
• 1 tsp Black pepper
• 25 g Cornflour
• 2 tsp Dijon mustard
• 600 g White fish fillet, skinless and boneless
• 10 g Fresh parsley

1. Heat the oven to 200°C (390°F). Peel the potatoes and cut into even chunks, then put into a large pot and cover with cold water; add 1 tsp of the fine sea salt.
2. Bring the potatoes to the boil, then simmer for 15 to 18 minutes until very tender. Drain well and leave in the hot pot for 2 minutes to steam-dry.
3. Mash the potatoes with 50 g of the butter and 150 ml of the whole milk until smooth. Season with a pinch of the black pepper and set aside.
4. In a saucepan over medium heat, melt the remaining 20 g butter. Whisk in the cornflour and cook for 1 minute until it smells lightly toasted but has not coloured.
5. Gradually whisk in the remaining whole milk until smooth, then bring to a gentle simmer and cook for 3 to 4 minutes until thick enough to coat the back of a spoon. Whisk in the dijon mustard, then season with the remaining fine sea salt and the rest of the black pepper.
6. Cut the white fish into large chunks and put into a baking dish. Finely chop the fresh parsley and stir most of it through the sauce, reserving a little for serving.
7. Pour the hot sauce over the fish and gently turn to coat. Spoon the mashed potato on top and spread to the edges to seal, then rough up the surface with a fork for extra browning.
8. Bake for 25 to 30 minutes until bubbling at the edges and lightly browned on top, and the fish flakes easily. Rest for 5 minutes, then sprinkle over the reserved parsley to serve.

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