Preheat oven to 350°F.
Remove the duck meat from the legs and breast. It should come to about 20 ounces total. Place the duck meat, bacon and ground pork in a food processor. Run the processor until all the meat is cut into small pieces. Transfer to a large bowl.
Add the shallots, parsley, salt, pepper, cognac and egg to the bowl and mix together until evenly combined.
Line the bottom of a 32 cm (12 – 13 inch) long terrine mold with a layer of the fatback (or bacon strips). Fill the terrine with your meat mixture, lightly pressing down to ensure you do not have any air pockets. Place the bay leaves on top and cover with the caul fat, tucking the edges of the caul fat into the sides of the terrine. If you cannot find caul fat then skip this step.
Place your terrine in a large roasting tin and place in the oven. Carefully fill the roasting pan with water until it reaches half way up the terrine. Cook in the oven for two hours, uncovered.
Carefully remove the terrine from its water bath and cover with a lid or aluminum foil. Weigh the lid down with some weights or something heavy (bricks work well, as long as they are wrapped in foil). Allow to cool, while weighted, for about one hour. Once cooled, remove the weights and lid and turn the pâte out of the terrine. Refrigerate until ready to serve.
To serve, cut the pate into slices and serve with cornichon and crusty bread.
Caul fat is a thin membrane that surrounds the internal organs in some animals, such as cows, sheep and pigs. It is often used as a casing for sausages or roulades or as a top layer for pâtes. It does not have much flavor so it’s primary purpose is either to hold something together or to provide some fat/moisture as the food cooks. If you cannot find caul fat, you can make the terrine without it.