Adjust oven rack to the top third level; heat oven to 300 degrees.
Line a baking tray with parchment paper (you'll use one tray per bake).
Toast nuts over low heat in a non-stick pan. When fragrant, transfer to a cutting board, mince and cool until ready to use.
In a stand mixer, beat sugars and butter until smooth then add miso paste and mix on low speed, just until combined.
Add egg, vanilla and baking soda; mix on low 1-2 minutes.
Slowly add flour and mix until just combined.
Remove bowl from mixer; stir in chocolate and nuts with a rubber spatula or wooden spoon.
Scoop 12 heaping tablespoons of batter onto the parchment-lined baking sheet.**
Bake 18-20 minutes, until nicely browned. Remove from oven and allow to cool 1-2 minutes on the baking tray, then transfer cookies to a cooling rack. Repeat. Makes 26-28 cookies.