1/4 cup (70g) prepared horseradish
Preparation time: 20 minutes(plus refrigeration time)
Combine horseradish and oil in large bowl: add beef, turn to coat in mixture. Cover; refigerate 3 hours or overnight.
Cook beef in heated oiled grill pan, turning, until browned all over. Reduce heat; cook beef, turning occasionally, about 30 minutes or until cooked. Cover, stand 10 minutes.
Meanwhile, combine ingredients for rocket salad in large bowl.
Combine mustard, parsley and breadcrumbs in small bowl with half the butter. Brush beef with remaining butter; press breadcrumb mixture over beef. Grill beef until crust is browned. Stand 10 minutes, slice thickly. serve beef with rocket salad.