Arrange the salmon steaks in a buttered flameproof baking dish just large enough to hold them in one layer, brush them lightly with some of the butter, and season them with salt and pepper. Pour the wine around the steaks and broil the steaks under a preheated broiler about 4 inches from the heat for 4 to 5 minutes, or until they are almost cooked through. While the steaks are cooking, stir together well the remaining butter, the bread crumbs, the horseradish, and the scallion, pat the crumb mixture evenly on the steaks, and broil the steaks for 2 to 4 minutes more, or until they are just cooked through and the crumbs are golden.
