Peel and finely chop the garlic and the onion.
Melt the butter in a large frying pan and then add the onions. Saute for about 2 minutes or until translucent and soft. Season with salt and pepper and then stir in the flour. Cook for 1 minute and then remove from the heat.
Heat the milk in a saucepan. Once it comes to the boil, add it to the onions and flour and whisk to make a smooth sauce. Return to a medium heat and cook until you have a thick, creamy sauce. Season with salt, pepper and nutmeg.
Pour the mixture into a baking tray or dish and chill in the fridge for 1 hour or until well chilled and easy to handle.
In a small mixing bowl, beat the eggs until frothy. Combine the bread crumbs and flour in a second bowl and season with salt and pepper.
Take handfuls of the cheesey mixture and roll into logs about 3/4 of an inch thick. Cut each roll into croquettes 1 and a half inches long. Dip each one into the egg wash, shake off the excess and then roll through the seasoned breadcrumbs. Place on a baking sheet and cover with cling film. Chill in the fridge for at least an hour.
Heat your deep fat fryer or a large pan of sunflower oil. Test that the oil is hot by adding a little bit of bread or one of the croquettes to the oil and it should sizzle when added. Add the croquettes to the pan in small batches and cook for 3 to 4 minutes or until golden brown. Once cooked, place on kitchen paper to get rid of excess oil.
«To give a really classical dish, try adding finely diced serrano ham.»