Peel and chop the 2 shallots. Chop the fresh parsley. Place the beef fillet (wrapped in bacon and tied) into an ovenproof dish. Season with salt and pepper. Sprinkle roughly with butter flakes. Top with chopped shallots and parsley. Bake at 250°C (482°F) for 20 minutes, basting 2-3 times.
Remove the fillet from the oven. Remove the bacon wrapping and twine. Roll the defrosted puff pastry to a thickness of 4 mm. Cover the fillet with the pastry. Bake at 250°C (482°F) for 20 minutes until the pastry is golden brown.