Cook the bacalao in a pan with water, olive oil, and salt for 7 minutes. Once cooked, shred the bacalao and set it aside.

In another pan, prepare the béchamel sauce. To do this, add the melted butter and stir in the flour until it forms a roux. Then, slowly pour in the milk until you achieve the desired texture. Add the ground nutmeg and pepper. Cook well until the desired flavor is achieved, adjusting the seasoning if necessary.

Sauté the onion and garlic in a pan with olive oil and let them brown well. Add the shredded bacalao and béchamel sauce and set aside.

For the pie crust, start by combining the salt and the butter. Using your fingertips, mix the butter with the flour until you get a sandy dough.

Place the flour mixture in a bowl, make a hole in the middle, and pour in a beaten egg and water. Knead the dough from the center outwards until it is well combined and smooth.

Grease a pie dish. Then roll out the dough and place it over the dish. Fill with the bacalao mixture and cover again with the dough on top. Crimp the edges to join the two pieces of dough and seal the pie.

Finally, brush the pie with one egg yolk and bake for 25 minutes at 180ºC.