Preheat your oven to 350F and place a sheet of parchment paper a large baking pan.
First, sift together the all-purpose flour, espresso, salt, and baking soda in a small bowl and set aside.
Then, melt the chocolate and coconut oil. Add a few inches of water to a small pan and bring to a simmer. In a separate heatproof bowl, add your chocolate chips and coconut oil. Set the bowl over the pan with simmering water and stir until completely melted and smooth. Remove the bowl of chocolate from the heat and let sit. It's also fine to microwave together in microwave safe bowl, stopping every 20-30 seconds to stir until completely melted.
Pour the melted chocolate and coconut oil into a large mixing bowl right after melting. Then, add the white sugar, brown sugar, flax egg, and vanilla bean paste to the bowl and whisk together until combined.
Gradually add the bowl of sifted dry ingredients to the larger mixing bowl with wet ingredients and mix until a smooth batter has formed. Use a spatula to scrape the sides and bottom of the bowl and mix one last time to make sure all the dry ingredients are evenly mixed. The batter will be soft and like a brownie batter at this point.
If you are adding chocolate chips to the cookies (highly recommended!), add the additional ¼ cup of chocolate chips and fold into the batter with a spatula.
Use a cookie/ice cream scooper to form cookie dough balls about 1 Tbsp in size and drop them onto the parchment paper. Make sure to leave enough space between each cookie as they will spread.
Bake for 8-9 minutes until cookies are crinkled on the outside, but still soft on the inside. Remove from the oven and let the cookies sit on the baking tray for at least 10 minutes to cool and firm u[ as they will be very soft. After that 10 minute mark, use a spatula to gently remove each cookie and place onto a cooling rack. Once cooled, top with extra flaky sea salt and enjoy!