Dice the butter, melt in a pan, chop the onion and garlic clove finely and add them to the butter.
Fry for 5-6 minutes, then add finely chopped Serrano ham, add flour and cook for about 5 minutes.
Pour in the milk slowly, stirring constantly. Boil the Béchamel sauce for 20 minutes, stirring constantly. At the end of cooking, add the chopped parsley.
When the dough has cooled down, you can form croquettes which should be oblong and about 5-6 cm long.
Then coat in flour, egg and breadcrumbs. Fry in well-heated, deep oil until golden brown. After frying, it is a good idea to drain excess fat from them.