Pulse until well blended and creamy, but not quite completely smooth. Stir in the remaining cup of chopped walnuts by hand and let cool.
Using a very sharp knife, slice diagonal cuts in the pastry about 1/2 inch apart on each side of the pate.
Bake until the pastry is puffed and golden brown all over.
Let cool for 5 minutes before slicing. Use a very sharp knife to slice with a sawing motion and gentle downward pressure; if you cut straight down, the filling is liable to squish right out the sides. Enjoy hot.