You will need
• 800g beef fillet, at room temperature
• 2 tbsp oil
• 2 tsp prepared English mustard
• 2 tbsp butter
• 1 onion, chopped
• 2 cloves garlic, chopped
• 250g Portabellini mushrooms, halved
• 2 tbsp chopped parsley
• salt and pepper
• 1 x 400g ready-rolled puff pastry, defrosted
• 1 egg, separated
• 2 tbsp milk (mix with yolk for egg wash)

1 Preheat the oven to 220ºC. Heat oil in a large, heavy-based pan and brown meat on all sides. Remove and set aside.

2 Melt the butter in a pan, add onion and garlic and cook for 1 minute. Add the mushrooms and the parsley and cook until all the liquid has evaporated. Remove, and allow to cool. Then, in a food processor, pulse until chopped but not smooth. Season.

3 Brush the beef with the mustard. Roll the pastry out onto a board lined with baking paper and spread evenly with mushroom mixture, leaving a border around the edges. Then place the beef on one half
of the pastry.

4 Roll the beef up in the pastry, leaving a small border. Brush the border with the egg white and seal well. Trim the ends off the pastry and pinch closed.

5 Decorate by cutting leaf shapes out of the leftover pastry and placing them on the Wellington. Brush with the egg wash and bake for 20–25 minutes. Allow to rest for 10 minutes before slicing. Serve with mixed roast baby vegetables.