Sift together flour, cocoa, and baking powder.

Working with a stand mixer, preferably fitted with a paddle attachment, beat the butter on medium speed until soft and creamy.

Add both sugars, the salt and vanilla extract and beat for 2 minutes more.

Turn off mixer. Pour in the flour mixture and manually incorporate it into the creamed butter and sugars, like you're cutting butter into biscuits. I do this until there are no more big swaths of dry ingredients waiting to create a dust-up.

For the best texture, work the dough as little as possible once the flour is added, and don't be concerned if the dough looks a little crumbly. Toss in the chocolate pieces and mix only to incorporate.

Turn the dough out onto a work surface, gather it together and divide it in half. Working with one half at a time, shape the dough into logs that are 1 1/2 inches in diameter. Wrap the logs in plastic wrap and refrigerate them for at least 3 hours or up to 3 days.

Preheat the oven to 325F. Have two lined baking sheets at hand.

Working with a sharp thin-bladed knife, slice rounds that are 1/2 – inch thick. (The rounds often crack as you’re cutting them – don’t be concerned, just squeeze the bits back onto the cookie.) Arrange the rounds on the baking sheets leaving about 1 inch of spread space between each round and slide one of the sheets into the oven. Bake the cookies for 12 minutes – they won’t look done nor will they be firm, but that’s just the way they should be.

Transfer the baking sheet to a cooling rack and let the cookies rest until they are only just warm, at which point you can serve them or let them reach room temperature. Repeat with the second sheet of cookies.