Beef Wellington

Ingredients

• For the Duxelles:
• 3 pints (1 1/2 pounds) white button mushrooms
• 2 shallots, peeled and roughly chopped
• 4 cloves garlic, peeled and roughly chopped
• 2 sprigs fresh thyme, leaves only
• 2 tablespoons unsalted butter
• 2 tablespoons extra-virgin olive oil
• Kosher salt and freshly ground black pepper
• For the Beef:
• 1 (3-pound) center cut beef tenderloin ( filet mignon), trimmed
• Extra-virgin olive oil
• Kosher salt and freshly ground black pepper
• 12 thin slices prosciutto
• 6 sprigs of fresh thyme, leaves only
• 2 tablespoons Dijon mustard
• Flour, for rolling out puff pastry
• 1 pound puff pastry, thawed if using frozen
• 2 large eggs, lightly beaten
• 1/2 teaspoon coarse sea salt
• Minced chives, for garnish