Heat 1 tbsp of the oil, in a large frying pan, add the pine nuts and cook over a low heat for 1-2 minutes, stirring or until pale golden. Remove from the heat, stir in the garlic and cool slightly.
In a bowl, mix the horseradish, stilton, breadcrumbs together with the pine nuts and garlic. Season with plenty of ground black pepper.
Wipe out the frying pan, then heat until very hot, add 1 tbsp oil. Add the beef fillet and cook for 2-3 minutes, turning until browned all over. Leave to cool.
Preheat the oven to Gas 6, 200°C, fan 180°C.
Spread the horseradish mixture all over the beef fillet.
Unroll the pastry; roll out on a lightly floured surface to a 35x25.5cm/14x10in rectangle. Place the beef in the centre. Brush the pastry edges with beaten egg, fold pastry around the beef and trim off the excess.
Pinch edges to seal. Place seam side down on a baking sheet. Cut pastry trimmings into leaf shapes; arrange on top. Brush with egg.
Bake for 40 minutes for medium-done beef. For well-done meat, cover with foil; cook for a further 10-15minutes.
Transfer to a platter; garnish with parsley and serve with green vegetables.
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Pair this with Chevalier du Tour Montagne Saint-Emilion
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For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.