Rinse the salmon fillet and pat dry.
Remove remaining bones and skin the fillet. Divide lengthwise and season on all sides with pepper and salt. Acidify with lemon juice. Place a strip of ham and Gouda on one half.
Place the second half on top and secure with toothpicks.
Build a breading line of flour, beaten egg and breadcrumbs. Dredge the prepared cordon bleu first in flour, then in egg and in breadcrumbs. Heat a frying pan with the clarified butter and fry the fillet in it until golden brown on all sides. Remove the toothpicks, arrange and serve.