Preheat oven to 325 F. Spray a cookie sheet (or two) with baking spray. In a medium saucepan, heat the butter and 1 cup of the chocolate chips over medium heat, until the mixture melts. Remove the pan from the heat and immediately stir in the brown sugar. Let the mixture cool slightly as you stir often.
Stir in the eggs and vanilla. Combine cocoa powder, flour and salt then stir this mixture into the batter in the bowl. Fold in the remaining chocolate chips.
Drop tablespoons of dough into the cookie sheet with about 2 inches of spaces in between. Bake for 10-12 minutes or until the cookie looks just about set in the edges and a little soft in the middle. Cool cookies completely on a wire rack.