Bacalhau com natas

Step 1: Put 1 ⅛ lb salt cod (bacalhau) skin side up in a large bowl of cold water, cover and keep it in the fridge for 24–48 hours, pouring off the water and adding fresh 3–4 times a day (thicker loins need the full 48 hours). Taste a flake from the thickest part: it should be pleasantly seasoned, not harsh. Never soak salt cod on the counter.

Step 2: Simmer the soaked cod in fresh water for 5 minutes until opaque and flaking. Drain, remove skin and bones and break into flakes.

Step 3: Heat 2 cups vegetable oil for frying in a deep pan to 350°F and fry 1 ¾ lb potatoes in batches for 5–6 minutes until pale gold. Drain on kitchen paper.

Step 4: Warm 3 tbsp olive oil in a large pan over a medium heat and cook 2 onions and 2 cloves garlic for 10 minutes until soft and lightly golden. Stir in the cod for 2 minutes. Heat the oven to 400°F (350°F fan).

Step 5: For the sauce melt 1 ⅜ oz butter, stir in 1 ⅜ oz plain flour and cook for 1 minute. Whisk in 2 cups milk a little at a time and simmer for 4 minutes until smooth and thick. Stir in ¾ cup single cream, 1 pinch grated nutmeg and ¼ tsp white pepper. Taste before salting; the cod brings its own salt.

Step 6: Fold the potatoes and cod mixture into two-thirds of the sauce and spread in a baking dish of about 30 × 20 cm. Pour over the rest of the sauce and scatter with 1 ⅜ oz grated cheese (such as mild cheddar). A common mistake is skipping the taste test: under-soaked cod can make the whole dish too salty.

Step 7: Bake for 25–30 minutes until bubbling at the edges and golden on top, and piping hot (167°F) in the centre. Rest for 10 minutes so it sets a little, then scatter with 1 tbsp parsley and serve. To make ahead, assemble, cool, refrigerate for up to a day and bake for 40 minutes.