Check that all bones have been removed from filets. In a small bowl, cream together butter and horseradish with a spoon. Stir in breadcrumbs and combine well. Season salmon and mound breadcrumb mixture on top and press down to cover top of salmon. Preheat broiler. Heat oil in nonstick skillet. Lay salmon pieces into skillet and cook over medium high heat until browned on bottom. Slide under broiler and cook for 3-4 minutes or until golden brown on top. Keep warm in oven until ready for service.