Creamy Salted Cod Gratin (Bacalhau às Natas Adaptation)

Roast the cubed potatoes in olive oil in the oven at 400°F (200°C) for 5 minutes.

Simmer the desalted cod loin with milk, garlic, and bay leaf until it boils again, timing 10 minutes of cooking after the boil.

Briefly sauté the onion in olive oil until wilted, then set aside.

Flake the cooked cod loin. Separate a portion of the flaked loin for an alternative version of the recipe.

Prepare the béchamel sauce by mixing butter and all-purpose flour. Incorporate the milk used for cooking the cod and cook until thickened.

Season the sauce with nutmeg, then add the heavy cream and yellow mustard.

In a separate bowl, whisk the egg yolk with the lemon juice. Incorporate this mixture into the hot sauce to add body and shine, ensuring the yolk does not fully cook.

Combine the partially roasted potatoes, sautéed onion, and flaked cod. You can gently mix everything, or layer it.

Top the mixture with the mozzarella and Parmesan cheeses.

Bake in the oven until golden brown and bubbly (au gratin).

Prepare the 'two-in-one' alternate version by finishing the reserved loin, potatoes, onion, and sauce, and drizzling with a thread of olive oil.