Heat oil in a pot and cook the flour, stirring constantly with a whisk. Once the flour is cooked, gradually add the milk, stirring as it incorporates.

Grate the Manchego cheese. When the béchamel sauce is thick, add the grated cheese, season with salt and pepper, and cook for a few seconds. Transfer to a container and cover with plastic wrap, pressing it directly onto the surface of the mixture.

Remove the crust from the stale bread and grate it using a coarse grater to make panko for the coating.

Take portions of the dough and roll them in flour to help shape the croquettes. Then dip them in beaten egg and coat with the panko. Fry in plenty of hot oil.