Preheat oven to 200°C
Pour olive oil, rosemary leaves and garlic into a pestle and mortar and bash the leaves to release all the oils.
Mix in contents of the KNORR Cheese & Bacon Flavour Potato Bake and add the mustard.
Rub the mixture over the beef fillet.
Place the fillet into a roasting dish and roast at 200°C for 30 min until medium rare, basting with the pan juices occasionally.
Remove from the oven and allow the meat to rest for 5 min before slicing.
Using a potato peeler, peel slices off the potatoes lengthwards, place in a bowl and pat dry.
Sprinkle with salt and mixed herbs.
Heat oil in a pot and fry the potato slices until they are golden brown and crispy.
Serve slices of fillet and herbed potato crisps together with roasted vegetables.