From: Art of Gluten-Free Baking
Preheat oven to 350 degrees F/180 degrees C/Gas Mark 4
Line a large cookie sheet with parchment paper.
In a medium bowl, mix together flour, cocoa, baking soda, and salt.
In a large bowl mix together butter, brown sugar, and granulated sugar. Stir together with a large spoon until smooth. Add vanilla, mix until combined. Add egg, mix until smooth. Add flour mixture, stir until smooth. Add chocolate chips and nuts, mix until smooth.
Drop by tablespoons onto the cookie sheet, leaving at least 1 1/2 inches between each blob.
Bake at 350 degrees for 16 minutes. Remove from oven, transfer cookies to a cooling rack.
Once completely cool, store in a tightly sealed container at room temperature for up to 5 days.