Preheat oven to 180C. Trim striploin of any fat. Heat a frypan on high heat and cook beef quickly for 3-4 minutes on each side. Transfer beef to an oven tray. Spread mustard over surface and roast for twenty minutes.
Remove beef and rest, covered for 5-10 minutes. Arrange combined salad ingredients in the centre of a large platter.
Thinly slice the beef and arrange around the salad Serves 4-5.