Prepare the Oven and Pan: Preheat the oven to 350°F (175°C). Line a 13 × 18-inch rimmed half-sheet pan with parchment paper, leaving a little overhang on two sides for easier lifting.

Lightly grease any exposed areas of the pan.

Combine the Melted Butter and Sugars: In a large mixing bowl, whisk together the melted butter, light brown sugar, and granulated sugar.

Continue whisking for about 1 minute. The mixture should look glossy and smooth, with no large lumps of brown sugar.

Add the Eggs and Vanilla: Add the vanilla extract and continue whisking until the mixture looks cohesive and slightly thickened.

Mix the Dry Ingredients: In a medium bowl, whisk together the flour, baking soda, and fine salt.

Make sure the baking soda is distributed evenly so there are no concentrated pockets in the finished bars.

Make the Cookie Dough: Add the dry ingredients to the butter mixture. Fold with a rubber spatula or sturdy wooden spoon just until no dry flour remains.

The dough should be thick, soft, and spreadable.

Add the Chocolate Chips: Reserve ½ cup (85 g) of the chocolate chips for topping.

Fold the remaining 2 cups (340 g) chocolate chips evenly through the dough.

Spread the Dough in the Pan: Transfer the dough to the prepared half-sheet pan. Use an offset spatula or clean hands to press it into an even layer all the way to the corners.

Take extra care not to leave the center substantially thicker than the edges.

Add the Remaining Chocolate: Scatter the reserved ½ cup (85 g) chocolate chips evenly over the surface.

Press them very lightly into the dough so they stay in place while baking.

Bake the Cookie Slab: Bake at 350°F (175°C) for 20–24 minutes. The edges should be golden brown and set, while the center should look lightly golden and no longer wet.

A toothpick inserted into the center should come out with a few moist crumbs but no raw dough.

Do not wait until the entire surface is deeply browned, as the bars will continue setting as they cool.

Cool in the Pan: Place the sheet pan on a wire cooling rack.

Let the cookie slab cool completely in the pan for about 45 minutes.

The center will firm as it cools, making the bars much easier to cut cleanly.

Slice and Serve: Use the parchment overhang to help lift the cooled cookie slab if desired.

Cut into 30 bars, arranging the cuts in a 5 × 6 grid.

Serve at room temperature.