Preheat oven to 300°F.
In medium bowl combine flour, cocoa, soda and salt. Mix well with a wire whisk. Set aside.
Blend sugars in a large bowl using an electric mixer set at medium speed. Add butter and mix to form a grainy paste, scraping down the sides of the bowl. Add eggs and vanilla, and beat at medium speed until smooth.
Add the flour mixture and chocolates, and blend at low speed until just combined. Do not over mix.
Drop by rounded tablespoons onto ungreased cookie sheets, 2 inches apart. Bake 18-22 minutes. Transfer cookies immediately to a cool, flat surface.