II
The Method
1
Combine the milk, jamón bone, and bay leaf in a saucepan. Warm over low heat until the milk steams but does not boil; remove from the heat and leave to infuse for 30 minutes. Strain and discard the solids. The milk should carry a distinct, savoury pork aroma before proceeding.
2
Melt the butter in a wide, heavy saucepan over medium heat. Add the flour and stir constantly for 2 minutes to cook out the raw flour. Begin adding the infused milk in a slow, steady stream, whisking continuously to prevent lumps. Continue cooking over medium heat, stirring without pause, until the béchamel is so thick that it pulls cleanly away from the pan sides and holds its shape briefly on the spoon — it must not drip. This is where the dish lives or dies: undercooking at this stage produces an interior that will collapse during frying.
3
Remove the pan from the heat. Fold in the finely minced jamón. Taste before adding any salt; the jamón provides the primary seasoning. Transfer the mixture to a shallow dish, press a sheet of cling film directly onto the surface to prevent a skin forming, and refrigerate until fully cold and firm — overnight is preferable.
4
With cold hands, portion the chilled béchamel and shape each croqueta to no longer than 6 cm. Lay them on a lined tray. Return to the refrigerator until firm again — they must be cold and set before breading.
5
Set up the breading station: flour, beaten egg, and fine breadcrumbs in three separate shallow dishes. Roll each croqueta in flour, shaking off the excess; pass through the beaten egg; coat thoroughly in fine breadcrumbs. For a sealed shell, repeat the egg and breadcrumb stages (double-breading). Arrange on a tray and refrigerate for at least one hour before frying.
6
Heat the frying oil to 185 °C in a deep, heavy pan. Fry the croquetas in small batches — never from frozen — turning once, until the exterior is deeply and evenly golden. The colour should be a uniform amber-brown with no pale patches. Drain briefly on absorbent paper.
7
Serve immediately. When a croqueta is bitten, the interior must flow — the filling should have reliquified completely under the fried shell. This interior fluidity is the defining quality marker of the dish.