3 1/2 pound center-cut beef fillet
salt and pepper
2 tablespoons olive oil
6 oz. paté
all-purpose flour, for dusting
1 17 1/4-oz. package puff pastry (thawed if frozen)
1 large egg, beaten
1. Set a wire rack on a rimmed baking sheet. Season beef with salt and pepper. Heat oil in a large skillet over high heat until hot. Brown beef all over, about 5 minutes total. Transfer to wire rack and let cool 10 minutes. Spread paté over fillet. Cover with duxelles, pressing into paté; set aside.
2. On a lightly floured work surface, overlap two puff pastry sheets by 1/2 inch. Roll out to a 12-by-20-inch rectangle. Place beef length-wise in the middle; wrap pastry around beef so long sides overlap. Place beef, seam side down, on a baking sheet, and tuck pastry ends underneath. Brush with egg. Refrigerate 30 minutes or up to 4 hours.
3. Preheat oven to 400 degrees. Bake pastry-covered beef until pastry is golden brown, approximately 30 minutes. Tent with foil and continue to bake until center of beef registers 130 degrees (about 15 more minutes). Transfer to a clean wire rack set over a rimmed baking sheet. Let stand 20 minutes before slicing.