Preheat the oven to 325F. Line a baking sheet with parchment paper.

Sift together the flour, baking powder, cocoa and salt. Set aside.

In a large microwave-safe bowl, place semisweet chips* and butter. Microwave for 20-30 seconds at a time, stirring after each time, until butter and chocolate are just melted and everything is blended.

Place the eggs, sugar and vanilla extract in the bowl of an electric mixer; beat about 4 minutes until soft and well blended, scraping down the sides of the bowl. Add the melted chocolate mixture and mix until blended, about 1 minute. Scrape down the sides of the bowl. Add the dry ingredients (and the remaining chocolate chips*) and mix on low just until blended, about 30 seconds.

Scoop cookie dough (about 3/4 oz.—I use a #40 scoop) onto cookie sheet, evenly spacing 12 cookies. Bake for 13-14 minutes. Remove the cookies from the oven and allow to cool to room temperature on the baking sheets, about 30 minutes. Store the cooled cookies in a tightly sealed plastic container until ready to serve.

* The original recipe called for about 2/3 of the chocolate chips to be melted with the butter and the remaining 1/3 of the chips added last to the cookie dough.