1. Preheat your oven to 400°F (200°C). Season the beef tenderloin generously with salt and pepper.
2. Heat olive oil in a heavy skillet over high heat. Sear the beef on all sides until it’s nicely browned, about 2-3 minutes per side. This step locks in the flavor and juices.
3. Remove the beef from the skillet and brush it all over with Dijon mustard. Set aside to cool.
4. In the same skillet, add butter and sauté the finely chopped mushrooms and garlic over medium heat. Cook until the mixture is dry and all the moisture has evaporated—about 10-12 minutes. Stir frequently to prevent burning. Add thyme if using.
5. Lay out a large piece of plastic wrap on your counter. Arrange the prosciutto slices in a slightly overlapping pattern to form a rectangle big enough to wrap around the beef.
6. Spread the mushroom mixture evenly over the prosciutto. Place the beef on top and, using the plastic wrap, roll the prosciutto and mushrooms tightly around the beef. Twist the ends of the plastic wrap to seal and chill in the refrigerator for 15-20 minutes. This step helps the Wellington keep its shape.
7. Roll out the puff pastry on a lightly floured surface. Remove the beef roll from the plastic and place it in the center of the pastry. Wrap the pastry around the beef, trimming any excess, and press to seal the edges. Use the beaten egg to brush the edges and seal completely.
8. Brush the entire pastry with the egg wash. If you want, use the back of a knife to gently score a pattern on top without cutting through the pastry—this adds a professional touch.
9. Place the Wellington on a baking sheet lined with parchment paper. Bake for about 25-30 minutes, or until the pastry is golden brown and crisp.
10. Let the Wellington rest for 10 minutes before slicing. This helps the juices redistribute and keeps the beef tender.

One thing I learned early on is to resist slicing too soon. My first attempt at Beef Wellington ended up a bit messy because I couldn’t wait to cut into it—lesson learned! Now, I always let it rest, and the results are so worth it.