Preheat oven to 350. Line cookie sheet with parchment paper. In large bowl combine flour, sugar, cocoa powder, baking powder, baking soda, and salt. Stir. In small bowl combine eggs, butter, and vanilla. Mix with electric or stand mixer on low speed. Slowly add flour mixture to egg mixture. Stir in chocolate & white chocolate chips. Roll out on floured surface into the shape of a 12 inch log. Place on parchment paper on cookie sheet. Bake for 25-28 minutes. Remove from heat and to wire rack. Cool for 30 minutes. Reduce oven heat to 300 and bake for an additional 15-20 minutes. Cool for 10 minutes. Serve or store in air tight container.