Preheat oven to 350°F (175°C). Line baking sheets with parchment paper or silicone mats.
Whisk flour, baking soda, and salt in a bowl; set aside.
In a large bowl, combine melted butter with brown and granulated sugars; whisk until smooth and glossy.
Add the egg, egg yolk, and vanilla to the butter-sugar mixture; whisk until well combined.
Gradually fold the dry ingredients into the wet until just combined; do not overmix.
Fold in 1 1/2 cups of the chocolate chips, reserving a few to press on top before baking.
Chill dough 30 minutes for thicker cookies (optional) or scoop immediately for thinner, chewier cookies.
Scoop rounds of dough (about 1½ tablespoons each) onto prepared sheets, spacing about 2 inches apart.
Press a few extra chocolate chips onto exposed tops of each dough mound.
Bake 10–12 minutes until edges are set and centers still look slightly underbaked; rotate pan halfway if needed.
Let cookies cool on the sheet 5 minutes, then transfer to a wire rack to finish cooling. Sprinkle with flaky sea salt if desired.