Whisk together the dry ingredients in a medium-sized bowl, and set the bowl aside.
In a large mixing bowl combine the melted butter, brown sugar, and white sugar. Beat until mixed together.
Add the large egg and vanilla extract. Mix until combined.
At low speed, add the dry ingredients to the wet ingredients until just combined together. Do not over-mix!
Fold in the dark chocolate chips. Cover the bowl with foil and refrigerate for 2 hours.
Preheat the oven to 350° F. Line two large baking sheets with parchment paper or foil, and set aside.
Line a cookie sheet with parchment paper. Use a 1-ounce cookie scoop to scoop the cookie dough out into 35-gram balls. Roll the dough with clean palms, and place each ball of dough 2 inches apart on the prepared sheet.
Bake for 8-9 minutes, or until the edges are just set and the centers have puffed up but are still gooey. For bakery-style cookies - Right out of the oven, place a large cookie cutter or round glass over the top of the freshly baked cookies, and swirl in a circular motion rounding them into perfect circles.
Sprinkle the cookies with flaky sea salt and allow them to rest on the baking sheet for 5 minutes, then transfer to a cookies rack for 1 hour to cool before storing.