Cook asparagus and keep it warm. Melt butter in top of double boiler over hot water; blend in flour with wooden spoon. Add milk and cream gradually; stir constantly. Cook over low heat until smooth and thick. Reserve 1 ts egg; add remainder to sauce; mix well. Place asparagus in serving dish; sprinkle with lemon juice. Pour sauce in gravy boat; sprinkle with reserved egg. Yield: 4 servings.