Heat oven to 350°F and line a baking sheet with parchment paper or a silicone baking mat.
In a large bowl, cream the butter and sugars together with an electric mixer with a paddle attachment until very light and fluffy, about 5 minutes. Add egg and vanilla, beating until incorporated, and scraping down the bowl as needed. Beat in salt (fine sea or table) and baking soda until combined. Add the flour on a low speed until just mixed. The dough will look crumbly. Stir in the chocolate chunks.
Using a cookie scoop, if you don't have a cookie scoop it's about 1 tablespoon mounds, spacing them apart on the prepared baking sheet. Sprinkle each with a few flakes of sea salt.
Bake for 10 minutes or until golden on the outside but still very gooey and soft inside. Once out of the oven, let the cookies rest on the baking sheet for 5 minutes. Transfer to a cooling rack.