Prepare the Mushroom Duxelles:

• Heat 1 tbsp of olive oil and 1 tbsp of butter in a large skillet over medium heat.

• Add the diced onion, garlic, and chopped mushrooms. Cook for about 5-7 minutes, until the mushrooms release their moisture and become tender.

Cook the Ground Beef:

• In the same skillet, heat the remaining olive oil over medium-high heat.

• Add the ground beef, breaking it up with a spoon as it cooks. Cook for 8-10 minutes, until the beef is browned and cooked through.

• Stir in the breadcrumbs, Dijon mustard, and the cooled mushroom mixture. Season with salt and pepper. Let the mixture cool to room temperature.

Assemble the Wellington:

• Preheat your oven to 400°F (200°C).

• Roll out the puff pastry on a lightly floured surface, ensuring it’s large enough to fully wrap around the beef mixture.

• Place the cooled ground beef mixture in the center of the pastry. Shape it into a log-like form.

• Fold the pastry over the beef mixture, sealing the edges and pinching the ends.

• Brush the top of the pastry with the beaten egg to give it a golden finish when baked.

Bake the Wellington:

• Transfer the wrapped Wellington to a baking sheet lined with parchment paper.

• Bake for 25-30 minutes, or until the puff pastry is golden brown and crispy.

• Let the Wellington rest for 5-10 minutes before slicing.

Serve: