In a stand mixer with the paddle attachment, cream the butter, granulated sugar, and brown sugar on medium speed until smooth and paste-like. Don't overcream; you want a smooth paste, like when making these thick chocolate chip cookies.

Beat in the eggs one at a time, then add vanilla extract. Scrape down the sides and bottom of the bowl to ensure all the butter has been incorporated.

Add the flour mixture to the butter mixture and mix on low speed until just combined. Fold in chopped chocolate pieces.

Use a cookie scoop to form 1/4-cup balls of dough. Place on a parchment-lined baking sheet and refrigerate for at least 8 hours or overnight. This step is crucial!

Preheat the oven to 375°F. Place chilled dough balls on parchment-lined baking sheets, spacing them 3 inches apart. Sprinkle them with flaky sea salt. Bake 12-14 minutes until edges are golden, but centers still look slightly underdone.

Let cookies cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.