Classic Beef Wellington

Ingredients

• 1 1/2 pounds (680 g) beef tenderloin, trimmed
• Salt & freshly ground black pepper, to taste
• 2 tablespoons (30 ml) olive oil
• 12 ounces (340 g) mushrooms, finely chopped
• 1 medium onion, finely chopped
• 2 cloves garlic, minced
• 3 tablespoons (45 g) unsalted butter
• 1 teaspoon (5 ml) fresh thyme, chopped
• 8 slices of prosciutto
• 1 package (14 ounces or 400 g) puff pastry, thawed
• 1 large egg, beaten (for egg wash)