Preheat the oven to 350 degrees F and line two baking sheets with unbleached parchment paper.

Best to whisk by hand. In a large bowl, whisk together the sugar, cocoa powder, salt, and arrowroot.

Add the egg whites and vanilla. Whisk until the batter forms into the consistency of a pourable fudge sauce. At first it will seem like the batter won’t come together, but it will. Do not overbeat. The batter will be runny. Stir in the nuts, chocolate chips or a combination of them.

Using a tablespoon size ice cream scoop, scoop mounds of chocolate batter onto the prepared baking sheets. They will spread so make sure to space them out at least 1-inch apart. Allow the batter to sit on the baking sheet at room temperature for 30 minutes before baking.

When ready to bake, sprinkle the top of the cookies with flaky salt. Bake cookies for about 12 minutes, until slightly puffed and the edges are crisp and the center is cracked and shiny. Cool completely on the sheet pan before transferring to a cooling rack. Store in a sealed container at room temp for up to one week.