Very closely adapted from Martha Stewart. Having made this recipe twice, I believe a good quality cocoa powder really makes a difference here. I definitely recommend Valrhona the most of the Dutched cocoas I have tried.
Whisk together flour, cocoa powder, baking powder, and salt in a medium bowl; set aside.
Put butter into the bowl of an electric mixer fitted with the paddle attachment. Mix on medium-high speed until pale and fluffy. Scrape sides and bottom of the bowl and add sugar. Beat again until light and fluffy. Repeat scraping as needed.
Add egg and vanilla; mix until creamy. Reduce speed to low. Add the flour mixture in 2 additions (scrape in between them) and mix until just combined. Fold in the mini chocolate chips by hand.
Cover dough with plastic wrap and let chill in the fridge for 30 or more minutes.
Preheat the oven to 375 F.
Using a 2 inch ice cream scoop or size-24 disher, drop dough onto baking sheets lined with parchment paper, 6 cookies per sheet. Using your hand, quickly and gently pat them slightly flat. Sprinkle coarse sugar (I used Swedish pearl sugar in the later pics) on top of the cookie dough and coarse sea salt if desired (the later pictures have sea salt).
Bake until edges are firm, 12-15 minutes. Let cool on sheets on wire racks. Cookies can be stored in an airtight container up to 2 days.