Crumble sausage into large skillet. Cook over medium-high heat until browned; drain well. Stir in eggs, cream, salt, mustard, 1/2 cup chesse and 1/2 can French fried onions; mix well. Pour into greased 8x12” baking dish. Refrigerate, covered, 8 hours or overnight.
Bake, uncovered, at 350° for 45 minutes or until knife inserted in center comes out clean. Top with remaining cheese and onions; bake, uncovered, 5 minutes or until onions are golden brown. Let stand 15 minutes before serving.
Makes 6 servings.