Hake croquetas with aioli

Method

1. Heat the 2 tbsp olive oil in a sauté pan over a low heat and gently fry the onion with the bay leaf for 15 minutes until really soft. Add the white wine and hake to the pan, then increase the heat and bring to a simmer. Cover and cook for 10 minutes.
2. Scoop out the hake and onion with a slotted spoon. Reserve 150ml of the cooking juices and set aside, discarding the bay leaf. Whizz the hake and onion in a food processor to combine.
3. To make the béchamel sauce, heat the 75ml olive oil in a saucepan over a medium heat and add the 75g flour. Cook for a couple of minutes, then gradually add the reserved cooking juices, followed by the milk, stirring continuously until you have a very thick, smooth sauce (about 15 minutes). Season well, then stir in the whizzed hake and onion. Spoon into a dish, then chill for at least 2 hours.
4. Once chilled, take spoonfuls of the mixture (about 30g each) and shape into an oval. Put the flour in one shallow dish, the egg in a second and the breadcrumbs in a third. Dust each croqueta with flour, then coat in egg and finally in breadcrumbs (see Know How). Put the croquetas on a baking sheet and chill until ready to cook (see Make Ahead).
5. Pour 1.2 litres oil into a large, deep saucepan and heat to 180°C or until a cube of bread browns in 30 seconds. Fry the croquetas a few at a time, cooking them for 2-3 minutes until golden brown all over and piping hot. Scoop out with a slotted spoon and set aside on a plate lined with kitchen paper. Sprinkle with sea salt, then repeat with the remaining croquetas. Serve with the aioli
   for dipping.
6. To make the aioli, whisk the egg yolk with the garlic, lemon zest and vinegar in a bowl. Season with a good pinch of sea salt. Slowly drizzle in the olive oil, whisking constantly, until you have a thick, luscious aioli. Add lemon juice to taste.