Heat the oven to 350°F (175°C). Grease a 13-by-9-inch baking pan or line it with parchment, leaving enough parchment overhang to help lift the cooled bars from the pan.

Cream the softened butter, packed light brown sugar, and granulated sugar until smooth and well combined. The mixture should look creamy and evenly blended rather than lumpy.

Beat in the eggs one at a time, mixing after each addition. Add the vanilla extract and stir until incorporated.

In a separate bowl, whisk together the all-purpose flour, baking soda, and salt. Gradually add the dry mixture to the butter mixture, mixing only until no dry streaks remain.

Stir in the semisweet chocolate chips until they are distributed throughout the dough. Avoid overmixing once the flour has been added.

Press the dough evenly into the prepared 13-by-9-inch pan. Use lightly greased fingertips or the back of a spoon to help spread the thick dough into the corners.

Bake for 25 to 30 minutes, until the edges are lightly browned and the center is set but still slightly soft. Do not wait for the center to look completely firm or the finished bars may lose their chewy texture.

Cool the pan on a rack for at least 30 minutes before cutting. Slice into squares once the bars have firmed, using the parchment overhang to lift them out if desired.