Preheat oven to 350 degrees Fahrenheit. Line a sheet pan with parchment paper.
Put dates and coconut oil into the bowl of a food processor or high-powered blender and puree until fully combined. A few small chunks of unblended dates are fine.
Add egg, vanilla, baking powder, baking soda, cinnamon, and salt, and process again to fully combine with the date mixture. Finally, add cocoa powder and flour and pulse just to combine.
Remove the blade from the food processor and use a rubber spatula to fold in the chocolate chunks, using this opportunity to scrape down to the bottom of the food processor and ensure that everything is fully mixed.
Scoop the cookie dough onto the sheet pan using a large cookie scoop (~3T each) to yield 10 total cookies. Slightly flatten each ball of cookie dough, since these will barely spread in the oven.
Bake for 8-10 minutes, or until cookies are slightly puffed up and just barely cooked through. Do not overbake these cookies or they take on a very dry, cake-like consistency. I recommend baking for 8 minutes exactly, and only adding an extra 1-2 minutes if absolutely needed.
Sprinkle cookies with flaky salt as soon as they come out of the oven (if using) and let cool on the pan for 5 minutes before transferring to a rack to cool completely. Leftovers can be kept in a sealed container at room temperature for 2-3 days.