Preheat the oven to 400 degrees F., and melt the butter in a 9×13 glass or ceramic baking dish. (It’s better not to use a metal pan as the wine may react with some surfaces.) Sprinkle the shallots evenly over the pan, separating the rings slightly.
Place the salmon in the dish, and pour the 1/2 cup wine overtop. In a small bowl, mix the mustard with the remaining 2 teaspoons wine, and then brush or evenly spread the mixture over the salmon. Sprinkle with the breadcrumbs, followed by the salt and pepper. (I sprinkle most of the salt over the salmon but do use a little to season the exposed shallots.)
Bake the salmon in the center of the oven for 13-15 minutes* or until the fish is mostly cooked but still a little rare on the inside. Switch to the broil setting and broil 6 inches from the heat, watching carefully, until the fish is just barely cooked through (it will continue to cook for a couple of minutes after removing from the oven) and the topping is golden.
Sprinkle with the parsley and serve with a lemon wedge for squeezing over the fish. You may also enjoy drizzling the pan juices over couscous, rice, baked potatoes, or sopping them up with a crusty roll.