1Place the fillet on a wire rack in a large roasting pan and roast
in a preheated 425F (220C) oven until it reaches an internal
temperature of 120F (48C), about 20 minutes. Remove from
the oven and let the meat return to room temperature. Meanwhile,
saute the shallot in the butter until tender but not browned, about
5 minutes. Add the chopped mushrooms and saute over high
heat, stirring frequently, until almost all of the moisture has
evaporated - the mixture should resemble a coarse paste.
Season with nutmeg, salt, and pepper, and allow to cool to room
2To assemble, roll out the sheets of puff pastry until they are
about 2 inches (5 cm) longer and wider than the fillet. Place the
fillet in the center of one of the sheets of puff pastry and spread
the pate de foie in a thin layer over the top and sides of the beef.
Top with the mushroom mixture. Brush the edges of the pastry
with water and place the second sheet of puff pastry over the top.
Trim and seal the edges, crimping with your fingers or the tines
of a fork. Decorate the top of the log with any remaining puff
pastry cut into decorative shapes and brush with the egg yolk
mixture. Bake in a preheated 425F (220C) oven for 10 minutes.
Reduce the heat to 375F (190C) and bake until the crust is
golden brown, about 20 minutes. Remove from the oven and
allow to rest 10 minutes. To serve, cut with a very sharp knife
into slices about 3/4 inch (2 cm) thick.