In a large bowl, whisk together the all-purpose flour, salt, and baking soda until completely uniform. Set aside.

Fix the paddle attachment onto an electric stand mixer. Drop the softened unsalted butter, dark brown sugar, and granulated sugar into the bowl. Beat on medium speed for 3 to 4 minutes until the mixture transforms into a pale, light, and fluffy paste.

Add the eggs one at a time, allowing the mixer to fully blend the first egg for 30 seconds before dropping in the second. Pour in the pure vanilla extract and beat for another 5 seconds to fully emulsify the liquids with the butter fats.

Turn the mixer down to its lowest speed. Add exactly half of the dry flour mixture and blend for 15 seconds. Stop the mixer, dump in the remaining flour, and mix just until the white streaks disappear. Do not overmix here, or the cookies will develop a tough, bready texture. Gently fold in the semisweet chocolate chips with a rubber spatula.

The Lipid-Solidification Chill: Cover the dough bowl tightly with plastic wrap and slide it into the refrigerator for a minimum of 6 hours (or up to 24 hours). Crucial: Do not skip this step. Aging the dough forces the dry flour starches to completely drink up the moisture from the eggs and vanilla. At the same time, it re-solidifies the creamed butter lipids. When the cold dough balls hit the hot oven, the solidified fat melts much slower, preventing the cookies from pancake-spreading and locking in an ultra-fudgy, dense center.

Preheat your oven to 375°F and line two large baking sheets with parchment paper.

Use your hands or a cookie scoop to shape the cold dough into compact 2-tablespoon-sized balls. Place them on the prepared baking sheets, leaving a 2-inch gap between each ball to allow room for natural expansion.

Bake for 12 to 14 minutes. Watch closely: you want to pull them out the absolute second the outer rims turn a deep golden brown, even if the tops look slightly pale and undercooked. Transfer the sheets to a wire rack to rest for 5 minutes—the trapped residual heat will finish cooking the centers on the tray—before moving the cookies directly onto the wire rack to cool completely.