1. Fill pot with enough water to cover the fish. Salt well and bring to a simmer.
2. Once simmering, place the cod in salted water. Cook 6-10 minutes, depending on the size of your fish fillets, until the fish is flaky but still firm. Remove from the water to cool.
3. Meanwhile, while fish is cooking, dice your onions and potatoes.
4. Refill (or top off) your pot with fresh water. Pour in potato chunks and bring to a boil. Boil about 20 minutes, until fork tender, longer if you like your potatoes more mashed than cubed.
5. Meanwhile, add 50g of butter and chopped onion to an enameled Dutch Oven or deep skillet. Sweat the onions in the butter for a few minutes, until translucent.
6. Sprinkle 50g of flour on top. Stir your roux until very thick.
7. Slowly stir in milk, whisking as you go to avoid lumps,
8. Simmer until the bechamel sauce is very thick. (When you drag your whisk across the bottom of the pan, it should take about 3 seconds to come back together.)
9. Season with salt, pepper, and a pinch of curry. (Start with a teaspoon of each and go from there.)
10. Drain the potatoes.
11. Stir in the broken up pieces of fish and potatoes.
12. Taste and adjust seasonings again.

Broil

1. Cover with a mild cheese and broil until golden and bubbly. (See note)