Preheat oven broiler.
Add the oil to a pot over medium high heat until hot but not smoking.
Add the shallots, cook until softened and slightly browned, about 3 minutes.
Add the soy, stout, molasses, smoked paprika,onion powder and chili powder. Bring to a boil, stirring occasionally until slightly thickened, about 6 minutes.
Line a baking sheet with aluminum foil. Spray lightly with cooking spray (or drizzle with vegetable oil.
Place salmon on the foil, skin side down.
Brush liberally with glaze.
Broil for 3 minutes, re-brush with glaze, and place under the broiler for 3 more minutes. Repeat (re-brushing and broiling) until the salmon is cooked through and flakes easily with a fork.
Serve over potatoes.