Chicken Croquettes (Croquetas de Pollo)

Method

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1. 1Melt the butter with the olive oil in a saucepan and soften the onion over low heat for 5 minutes without colouring. Add the chicken and stir for 1 minute.
2. 2Add the flour and cook for 2-3 minutes, stirring constantly; it should lose its raw smell and smell slightly nutty without taking on colour.
3. 3Add the cold milk a little at a time, whisking after each addition until there are no lumps. Season with salt, pepper and nutmeg.
4. 4Cook over low heat for 10-12 minutes, stirring constantly with a wooden spoon. The béchamel should become very thick, pulling away from the sides of the pan, with a line drawn by the spoon not closing straight away.
5. 5Spread the mixture in a greased dish, cover with cling film pressed onto the surface so no skin forms, and chill for at least 4 hours, ideally overnight.
6. 6With lightly wet or oiled hands, take walnut-sized pieces and shape them into small logs. Roll in beaten egg, then breadcrumbs, making sure there are no gaps.
7. 7Heat the oil in a deep pot to 180 °C. Fry the croquettes in batches of 4-5 for 2-3 minutes until golden all over, drain on paper towels and serve hot.