In a small heavy saucepan over LOW heat, melt unsweetened chocolate, butter, and 1 cup of the semisweet chocolate pieces. Stir occasionally and continue to cook until the chocolate has completely melted. Remove pan from heat and allow mixture to cool for about 30 minutes.
Preheat oven to 350 degrees F. Line baking sheets with parchment paper.
In a medium bowl, combine flour, cocoa powder, baking powder, and salt. Set aside
In a large bowl beat together sugar, eggs, and vanilla with an electric mixer for about 2 minutes. Add the cooled chocolate mixture and beat until combined. Mix in the flour mixture with a wooden spoon. Add the remaining semisweet baking pieces and the pecans. Mix well to combine.
Place small balls of dough, approximately 1-inch in diameter, on the parchment paper lined baking sheets. Use your hands to round them but leave them somewhat roughly shaped. Bake for 8 to 9 minutes or until they appear to be set. Be careful not to overcook. They will set up more as they cool.
Allow cookies to cool on baking sheet for a minute or two and then transfer to wire racks to cool completely.
Store cooled cookies in an airtight container.