- Season the foie gras with 2 teaspoons of the salt and 1 teaspoon of the cracked pepper. Put them in a large plastic storage bag or a large shallow plastic bowl. Pour in the port wine. Refrigerate for 12 hours, turning them about every 2 hours.
- Remove the foie gras from the bags or bowl and discard the marinade.
- Season the foie gras with the remaining 2 teaspoons salt and 1 teaspoon cracked pepper. Cut each diagonally into 4 pieces, each about 1 inch wide.
- Line a classic terrine mold (12 x 4 x 2 1/2 inches) with a sheet of plastic wrap, leaving enough to overlap the edges by about 3 inches.
- In a large skillet over high heat, sear the foie gras, 4 to 5 pieces at a time, browning them evenly, 30 to 45 seconds per side. Drain the fat from the skillet after cooking each batch and strain it through a fine-mesh sieve into a bowl.
- Arrange a layer of the seared foie gras in the bottom of the prepared terrine. Pour about 1/2 cup of the strained fat over the layer of foie gras. Arrange the next batch of foie gras in another layer, pressing it down gently but firmly so that there are no air pockets. Repeat the process until all the pieces are in the terrine. Reserve 1/2 cup of the remaining strained fat and discard the rest. Refrigerate the fat.
- Fold the plastic wrap tightly over the foie gras. Wrap the entire terrine tightly with another large sheet of plastic wrap. Weight the top with a brick or two wrapped in aluminum foil. Refrigerate for 12 hours.
- Remove the terrine from the refrigerator and briefly submerge the bottom in hot water, then carefully lift it out of the mold, grabbing the plastic wrap. Melt the reserved 1/2 cup fat and generously brush the sides, top, and bottom of the terrine. Wrap the terrine tightly in fresh plastic wrap, and refrigerate for 12 hours more.
- To serve, cut into 1/4-inch-thick slices. Serve with the croutons and drizzles of the port wine reduction.