Filet De Boeuf En Croute (Beef Wellington)

Preparation

1. Step 1

   A day ahead, make the pastry. Place flour into a food processor. Cut the butter into tablespoon-size pieces and drop one by one into the flour to coat. Pulse about 5 times until butter is finely chopped. Combine the eggs, oil, 1 tablespoon water and the salt and blend with a fork. With the food processor running, pour the egg mixture in and process until dough starts to form. Stop and scrape the sides and bottom. Process just until the dough forms shiny, damp clumps, adding about 1 tablespoon more water if necessary. Turn out onto a work surface and knead lightly to make a smooth ball. Flatten into a 1½-inch-thick rectangle. Cover with plastic wrap and place in a food-storage bag. Refrigerate overnight.

2. Step 2

   The next day, let the dough set at room temperature for about 15 minutes. Meanwhile, sprinkle the fillet with salt and pepper. Spread the ground sausage on top, sprinkle with the truffle pieces (if using) and pat them into the sausage.

3. Step 3

   Roll out pastry on a lightly floured work surface. Place the fillet, sausage side down, almost in the center of the dough. Beat 1 egg yolk with 1 teaspoon water. Fold up one long side of the pastry so that it almost covers the bottom of the fillet. Brush 1½ inch of the long edge with some egg-yolk mixture. Trim the other long edge so that it just reaches over the brushed portion, and fold it up. Press lightly to seal. Flip the pastry-wrapped fillet. Seal the ends, moistening them with yolk mixture so they stick together.

4. Step 4

   Place on a rimmed baking sheet. Brush pastry twice with the remaining egg-yolk mixture. Cut several slits in the top for air vents. Refrigerate while preheating the oven.

5. Step 5

   Preheat oven to 400 degrees. Bake fillet until the internal temperature registers 135 degrees on an instant-read thermometer, about 35 minutes for medium-rare. If the pastry browns too quickly, cover loosely with a piece of parchment paper.

6. Step 6

   Let fillet cool for 15 minutes before cutting it into thick slices. Serve warm.