In a medium bowl, sift the flour, cocoa powder, baking powder, and baking soda, and set aside.

In the bowl of a stand mixer  with the paddle attachment, cream butter, coconut oil, both sugars, and salt. 

Cream on medium speed until pale and fluffy, it typically takes 1-2 mins

 Add the egg, and mix until combined.

On low speed, add the flour mixture, and mix to incorporate. Mix in the chocolate and ginger until just combined.

Turn the dough out onto a sheet of plastic wrap. Press and shape to form a 1-inch-thick rectangle, and wrap tightly. Refrigerate for at least 3 hours.

For baking :

Preeheat the oven to 375°F

Line 2 large baking sheets with parchment paper. 

Lightly flour a work surface and place the dough on top. Slice into 12 equal pieces. Roll each piece into a ball and transfer to the prepared sheets, leaving at least 1 inch between each. 

Sprinkle with sea salt.

Bake until the edges have crisped slightly, 10–12 minutes. Remove and let cool for 5 minutes on the baking sheets, then transfer to a rack to cool completely.

Dont be tempted to bake longer, trust me this time is enough