Heat a frying pan and add a little olive oil. Season the beef and sear in the hot pan for 30 seconds only on each side to colour. Leave to cool and then brush all over with the whole grain mustard.
Roll out the puff pastry on a lightly floured surface to a large rectangle and place the beef in the centre. Brush the surrounding pastry with the egg yolk and wrap the pastry round the beef and cut off any excess. Turn over and place on a baking sheet and brush with the rest of the egg.
Sprinkle the spices and parmesan over the surface and rest in a fridge for 30 minutes, heat oven to 200°C/Gas mark 6. Bake for 20 minutes and then lower the oven to 180°C/Gas mark 4 and cook for a further 15 minutes and then take the beef out and rest for 15 minutes. The beef should be pink when you serve it.
For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home.