Sauteé onions until caramelized, add mushrooms. Sauteé 2 minutes add all three broths. Increase heat to boil. Reduce heat to medium. Whisk with one tbs roux until well combined. Allow to tighten up. Add more roux as needed to thicken up. Sauce should not be goopy thick nor ultra thin. Sauce should coat nicely, but still flow freely. Which with heavy cream. Adjust with salt and pepper.
Salt and pepper salmon fillets. Combine ingredients 2-8 thoroughly. Dredge in all purpose flour, egg wash, bread crumbs mixture.
Pan fry in 1/2 inch of cooking oil until desired doneness is achieved. Top with Marsala sauce.