Fry in a pan with a little fat, then place in a bowl and keep warm.
Briefly sauté the onion brunoise in the same pan, add the cream, add the mustard. Let it simmer until you get the consistency you want. Possibly re-tie with sauce binder (light).
Season the “cream” and add the meat. Refine with butter.
Finally sprinkle with parsley (freshly chopped).
It goes well with croquettes, wedges and risolle potatoes.