Follow these steps to create the perfect Halal Beef Wellington:

Preparing the Beef:

1. Season the Beef: Begin by seasoning the beef tenderloin with salt and black pepper. Pat it dry with paper towels to ensure a nice sear. Then, brush the entire surface with Dijon mustard. This helps to enhance the flavor of the beef and allows the seasonings to adhere better.
2. Sear the Beef: Heat 2 tablespoons of olive oil in a large skillet over medium-high heat. Once hot, add the beef tenderloin and sear on all sides for about 3-4 minutes per side, or until a rich brown crust forms. This will help lock in the beef’s juices and flavor. Remove the beef from the skillet and allow it to cool to room temperature.
3. Chill the Beef: Place the beef in the refrigerator for at least 15 minutes to allow the mustard and sear to set. This will help when wrapping the beef in the pastry.

Preparing the Mushroom Duxelles:

4. Cook the Mushrooms: While the beef cools, finely chop the mushrooms into small pieces, either by hand or using a food processor. This ensures that the duxelles filling is smooth and evenly distributed inside the Wellington.
5. Sauté the Duxelles: In a skillet, melt the butter over medium heat. Add the finely chopped onions and sauté until translucent, about 3 minutes. Add the garlic and cook for an additional minute, until fragrant. Then, add the chopped mushrooms, salt, and pepper. Stir occasionally and cook the mushrooms until most of the moisture has evaporated and they become a paste-like consistency, about 10-15 minutes.
6. Finish the Duxelles: Add the thyme and parsley (if using) to the mixture. Stir well, then remove from heat. For extra richness, add a tablespoon of heavy cream. Let the duxelles cool to room temperature before proceeding to the next step.

Assembling the Beef Wellington:

7. Prepare the Puff Pastry: Lay a large sheet of parchment paper on your work surface and unroll the puff pastry. Lightly flour the surface to prevent sticking. The pastry should be large enough to fully enclose the beef. You may need to roll it out a little further to ensure it can wrap around the entire beef.
8. Spread the Duxelles: Once the beef and mushroom duxelles are both cooled, spread the mushroom mixture evenly over the top of the beef tenderloin, ensuring it is fully covered.
9. Wrap the Beef: Carefully place the beef, now coated in duxelles, onto the center of the puff pastry. Gently fold the pastry over the beef, making sure it is fully enclosed. Pinch the seams and edges to seal the pastry. If desired, you can trim any excess pastry to create a more polished appearance.
10. Brush with Egg Wash: Place the wrapped Beef Wellington seam-side down onto a baking sheet lined with parchment paper. Brush the top of the pastry with the beaten egg to give it a golden, glossy finish when baked. For added visual appeal, score the top of the pastry lightly with a knife to create an elegant pattern.

Baking the Beef Wellington:

11. Bake the Wellington: Preheat your oven to 400°F (200°C). Place the Beef Wellington into the oven and bake for 35-40 minutes, or until the pastry is golden brown and crisp. The internal temperature of the beef should reach 125°F (52°C) for medium-rare. If you prefer a different level of doneness, you can adjust the baking time accordingly.
12. Rest the Wellington: After removing the Beef Wellington from the oven, allow it to rest for 10 minutes before slicing. This will help the juices redistribute within the beef, ensuring a moist and tender result.

Serve and Enjoy:

13. Slice and Serve: Carefully slice the Beef Wellington into thick slices and arrange on a serving platter. Pair it with your favorite sides, such as mashed potatoes, roasted vegetables, or a green salad for a complete meal.