Chop walnuts extremely finely. In a microwave or double-boiler, melt chocolate chips, condensed milk, and 1 tbsp butter, mixing occasionally, until well mixed to a chocolate frosting consistency. Add nuts, mix, and cool.

In a separate bowl, cream the rest of the butter with the brown sugar, then add the vanilla extract, flour, and salt. The dough should be rather crumbly. If necessary, add the milk or water to make it hold better. Divide the dough into three equal parts. Roll out onto waxed paper or plastic wrap, making a rectangle two to three times as long as it is wide. You may chill the dough if it makes it easier to work with.

Spread a third of the chocolate mixture onto each dough section, and roll into a jellyroll shape. Bake at 350F for approximately 30 minutes, until light brown. Cool.

Slice each log into slices between 1/2" and 1" in thickness. If you want to keep them longer, don't slice the log until ready to serve. The pieces never last long, though, so I wouldn't worry!