Preheat oven to 350ºF. Line two baking sheets with nonstick silicone mats or parchment paper.
In a large bowl, combine cashew butter, coconut sugar, egg and baking soda. Use a wooden spoon or sturdy spatula to mix until evenly combined and no large streaks of cashew butter remain. Fold in ¾ of the chocolate (about 4 ounces).
Use a large cookie scoop (about 1 ½ Tablespoons) to portion out balls of dough onto prepared baking sheets. You want to give the cookies room to spread, so I recommend no more than 6 per baking sheet (though you can probably fit up to 8 if need be).
Press remaining chocolate pieces into the tops of each cookie and sprinkle with sea salt.
Bake each batch for 11 minutes, or for a few minutes longer if you prefer a more crisp cookie. They will be soft when removed from the oven, and will crinkle and flatten as they cool - let cool completely on the baking sheet* (about 20 minutes). Serve and enjoy!
Store in an airtight container at room temperature or in the fridge.
*I'm serious. Really let them cool completely, as they will set as they cool and could fall apart on you if you try to remove them sooner.