• Preheat your oven to 350°F. Line a baking sheet with parchment paper. Set aside.
• In a mixing bowl, beat together the butter, sugar, salt, vanilla extract, and baking powder until well combined and creamy.
• Beat in the eggs.
• Add the flour and beat until just mixed in.
• Lastly, stir in the walnuts.
• Turn the dough out onto a prepared baking sheet and form it into a log. (Dust your hands with cocoa; dough is a bit sticky!)
• Form the log into a rectangle shape that is roughly 4" wide and 12" long.
• Bake for 30 minutes. Remove from the oven and place the baking sheet on a wire cooling rack so that air can circulate. Allow to cool for 5 minutes.
• Using the parchment paper, slide the log onto a large cutting board. Slice into 1/2" slices across the width of the log.
• Place slices back onto a parchment-lined baking sheet, cut side down. Bake for 10 minutes. Flip the biscotti over and bake for 10 minutes more.
• Remove from the oven and allow the biscotti to cool on the baking sheet for 3-5 minutes. Transfer to wire cooling rack to finish cooling completely.

For the Optional Glaze:

• Whisk the confectioner's sugar and milk together until smooth. With all of the biscotti standing on end on a wire cooling rack with a catch tray underneath, use a spoon to spoon the glaze over the tops of the biscotti, allowing the glaze to trickle down the side. Allow the glaze to fully harden before packaging.
• Package biscotti for gift-giving or pile into a food-safe container. Leave at room temperature, or freeze until needed for up to 3 months.