Prepare two baking sheets with parchment paper or silicone baking mats. Heat the oven to 325ºF. You will be using two shelves.
Put the olive oil, brown and white sugars and the egg into a medium bowl and beat on high with an electric mixer for one minute.
Sift the cocoa and flours into the bowl, then add in the vanilla, salt and baking powder, and stir together by hand using a wooden spoon. The batter will be very stiff and stubborn—keep going until everything is well mixed. Then add in the chopped chocolate and stir together until everything is evenly mixed.
To make the balls of cookie dough, measure out 3 tablespoons of the dough and roll into an approximate ball. Place on a cookie sheet and flatten very slightly. If you like, press in one or two extra chunks of chocolate into the center top. I used chunks that had fallen out of the dough during the ball-rolling process. This recipe should make about a dozen three-inch cookies (see Kitchen Notes).
Put both cookie sheets in the hot oven, one on each shelf, and set a timer for 8 minutes. When it sounds, switch the cookie sheets, and set the timer for another 8 minutes.
The cookies are ready when the outer edges start to set—if you lightly press the edges, they will feel a bit stiff, but will slightly give away. Take the sheets out of the oven and set them on the stovetop or on racks on the counter—let them cool on the sheets, not on racks, for 15 or 20 minutes before trying to pick them up.