Preheat oven to 350° F and place rack in the middle of the oven.
Spread the nuts on a baking sheet and toast them in oven until lightly golden. Let cool. Coarsely chop half the nuts.
In bowl of stand mixer, combine flour, sugar, salt and baking soda.
Beat in eggs, then stir in the whole and chopped nuts. Mix to obtain a firm dough. NOTE: Dough should be sticky, but should not appear wet. You can add a little extra flour if necessary, but only a tablespoon at a time.
On a floured work surface, knead the dough briefly, then divide it into 2 pieces. Roll each piece under your hands into a cylinder 15 inches long and about 1-½ inches in diameter. Place the rolls, well separated, on baking sheet and bake 20 to 25 minutes, until very lightly browned and firm to the touch. The dough will spread a bit during baking.
With a spatula, carefully transfer the rolls to a cutting board and slice each one diagonally about ½-inch thick. Remove the parchment paper and set the wire rack on the baking sheet, and then lay out the biscotti on the rack. Return to the oven for 20 to 25 minutes, or until very firm and crisp.
Cool on the rack, then dip the ends of the biscotti into the melted chocolate. Lay them on a piece of parchment or wax paper and allow the chocolate to firm up. Store in an airtight container.