Heat oven 400 degrees
Combine butter and brown sugar in a bowl and microwave until the butter and sugar has melted together, about 30 seconds.
Stir in the mustard, honey and soy sauce.
Toss the asparagus with 1 tablespoon of the oil, the parmesan cheese, and some salt and pepper. Place the stalks in a baking dish and roast until they're al dente, 10 to 12 minutes.
Meanwhile, heat the remaining tablespoon of oil in an ovenproof skillet over high heat. Season the fillets with salt and pepper and add them to the pan.
Cook until brown on one side, 3 to 4 minutes, then flip them over. Brush on half the honey mustard and place the pan in the oven.
Bake until the salmon is firm and flakes easily (but before white solids begin to form on the surface, about 5 minutes.)
Remove the filets from the oven and brush them with more honey mustard. Serve the salmon with asparagus.