Created by breezermom on December 10, 2016
Step 1: Cook the potatoes, covered, in boiling water to cover for 20 minutes or until tender; drain and let cool slightly. Cut the potatoes into 1/2 inch thick slices; layer slices in a greased 2 quart baking dish. Set aside.
Step 2: Saute the onion in butter in a large skillet until tender; add flour, stirring until smooth. Cook 1 minute, stirring constantly. Gradually add the broth; cook over medium heat, stirring constantly, until the mixture is thickened and bubbly.
Step 3: Remove from heat, and stir in the mustard, horseradish, and pepper.
Step 4: Pour the sauce over the potato slices; sprinkle with breadcrumbs. Bake, uncovered, at 375° for 20 minutes or until thoroughly heated.