Stir together flour, salt, and brown sugar. Cut in butter till mixture is crumbly. Add eggs and mix well with your hands. Mix in 1 1/2 cups of the chips and the 1 cup nuts.
Set aside 1 1/2 cups of the dough.
Press the remaining dough into a greased 9x13" pan. Bake at 350° for 10 minutes.
Pour the sweetened condensed milk evenly over the crust. Top with all but 1/4 of the toffee bits. Place pieces of remaining dough over the top. Sprinkle with remaining 1/2 cup chips.
Bake for 25-30 more minutes, or till golden brown. Sprinkle the remaining 1/4 cup toffee bits on top.