In a large, microwave safe bowl, melt the butter and 1 cup of the chocolate chips at 50% power, stirring every minute, until melted and smooth. Cool to room temperature.

Add the brown sugar, eggs and vanilla to the chocolate mixture and stir until well combined.

Stir in the flour, cocoa powder, salt and baking soda until just combined. Fold in the remaining 1/2 cup chocolate chips. Chill dough for at least one hour.

Meanwhile, preheat oven to 350 degrees. Line two large baking sheets with parchment paper.

Roll cookie dough into walnut-sized balls and place a few inches apart on prepared baking sheets. Bake for 8-10 minutes, or until set on the edges but still soft in the middle. Do not overbake.

Remove from oven and cool on baking sheets for 3-5 minutes before removing to wire racks to cool completely.