Instructions:

1. Preheat the Oven: 🔥 Preheat the oven to 400°F (200°C).
2. Prepare the Beef: Season the beef tenderloin with salt and pepper. 🧂 Heat olive oil in a pan over high heat and sear the beef on all sides. Once browned, set aside to cool. 🥩
3. Apply Dijon Mustard: Spread Dijon mustard evenly over the beef. 🧴
4. Prepare the Mushroom Mixture: Sauté mushrooms 🍄, onion 🧅, garlic 🧄, and thyme 🌿 in butter 🧈 until soft and all moisture is evaporated. Let it cool.
5. Prepare Prosciutto: Lay out plastic wrap and arrange prosciutto 🥓 slices in overlapping layers. Spread the cooled mushroom mixture evenly over the prosciutto.
6. Wrap the Beef: Place the beef on top of the mushroom-covered prosciutto and roll it up tightly using the plastic wrap.
7. Wrap in Puff Pastry: Roll out the thawed puff pastry 🥐. Unwrap the beef from the plastic wrap and place it in the center of the pastry. Wrap the beef in the pastry and seal the edges.
8. Egg Wash: Brush the pastry with beaten egg yolk 🍳 to give it a golden finish when baking.
9. Bake: Place the wrapped beef on a baking sheet and bake for 30-35 minutes or until golden brown and cooked to your desired doneness.
10. Serve: Let the Beef Wellington rest for a few minutes before slicing. Serve warm and enjoy! 🎉