Best Beef Wellington Recipe - How to Make Beef Wellington

Ingredients

• 1 (2 lb.) center-cut beef tenderloin, trimmed
• Kosher salt
• Freshly ground black pepper
• extra-virgin olive oil, for greasing
• 2 tbsp. Dijon mustard
• 1 1/2 lb. mixed mushrooms, roughly chopped
• 1 shallot, roughly chopped
• Leaves from 1 thyme sprig
• 2 tbsp. unsalted butter
• 10 thin slices prosciutto
• all-purpose flour, for dusting
• 14 oz. frozen puff pastry, thawed
• 1 large egg, beaten
• Flaky salt, for sprinkling