Croquetas de Jamón

Method

1. 1Dice the jamón into 3 to 4 mm pieces. Melt the butter with the olive oil in a wide heavy pan over medium heat, add the ham and fry it for 2 minutes, until the fat renders and the pan smells toasted rather than raw.
2. 2Add the finely chopped onion with a pinch of salt and cook 8 to 10 minutes over low heat until it is soft and translucent without taking any colour. Browned onion shows up later as dark specks and a caramel note that does not belong here.
3. 3Add the 120 g of flour all at once and cook it 5 to 7 minutes over low heat, stirring constantly, until it turns the colour of pale sand and no longer smells of raw flour. This step is the single biggest cause of pasty croquetas when it is cut short.
4. 4Heat the milk until it is steaming but not boiling, then add it in five additions, whisking each one in completely before the next so no lumps form. Season with the nutmeg and the salt.
5. 5Switch to a wooden spoon and cook 25 to 30 minutes over low heat, stirring constantly and scraping the base, until the mass comes away from the pan in one piece and a line drawn with the spoon holds for about 2 seconds before closing.
6. 6Spread the dough about 2 cm thick in a tray, press cling film directly onto the surface so no skin forms, cool to room temperature and refrigerate at least 4 hours, preferably overnight. Warm dough cannot be shaped and will split in the fryer.
7. 7Shape about 20 pieces of roughly 35 g, roll each in flour, then beaten egg, then breadcrumbs, pressing firmly so the coating has no gaps. Fry at 175 °C in batches of five or six for 2 to 3 minutes, until deep gold, drain on a rack and wait 2 minutes before eating, because the inside comes out molten.