In the mixing bowl, combine cocoa and baking soda. Add ⅓ cup melted butter and the boiling water and stir on low until the mixture thickens.
Stir in sugar, eggs, and remaining ⅓ cup melter butter. Mix until smooth.
Add the flour, vanilla, and salt, and mix completely. Stir in nuts or chips, if desired.
Pour into the prepared pan. Bake for 30 to 35 minutes or until brownies pull away from the sides of the pan, but watch them carefully after 30 minutes to make sure they don't over bake. Cool completely in the pan. Cut into bars.
You can find this recipe at https://andreasrecipes.com.