Beef Wellington in Puff Pastry

Heat 1 tbsp olive oil in a skillet over high heat. Season the beef tenderloin generously with salt and pepper. Sear the beef on all sides for 2-3 minutes until a nice crust forms. Remove from the skillet, brush with Dijon mustard, and let it cool completely.

Clean and finely chop the mushrooms (a food processor works well). In the same skillet, melt 1 tbsp butter and 1 tbsp olive oil over medium heat. Add the finely chopped shallots and garlic, sauté for 2-3 minutes. Add the chopped mushrooms and thyme, then cook until all the liquid has evaporated and the mushrooms are dry and paste-like (about 15-20 minutes). Season with salt and pepper, then set aside to cool.

Lay out a sheet of plastic wrap on a clean surface. Arrange the prosciutto slices, slightly overlapping, to form a rectangle. Spread the cooled mushroom duxelles evenly over the prosciutto. Place the cooled, mustard-coated beef tenderloin in the center of the mushroom layer. Using the plastic wrap, tightly roll the prosciutto and duxelles around the beef, then wrap it tightly. Refrigerate for at least 30 minutes, or up to 1 hour.

On a lightly floured surface, roll out the puff pastry (if using two sheets, slightly overlap and press the edges together). Remove the beef from the refrigerator and unwrap the plastic. Place the beef in the center of the pastry and carefully wrap it, trimming any excess pastry and sealing the edges. Flip it over so the seam is on the bottom. Decorate the top of the pastry with a sharp knife or fork, but do not cut all the way through. Brush with the beaten egg.

Preheat your oven to 200°C (180°C for fan-assisted ovens). Place the Beef Wellington on a baking sheet lined with parchment paper. Bake for 30-40 minutes, or until the pastry is golden brown and crisp, and the internal temperature of the beef reaches your desired doneness (52-55°C for medium-rare). Remove from the oven and let it rest for 10-15 minutes before slicing. Then slice and serve immediately.