Preheat your oven to 350°F (175°C). Grease a 9x13 inch baking pan thoroughly. You can also line it with parchment paper for easy removal.

In a large mixing bowl, combine the melted unsalted butter, packed light brown sugar, and granulated sugar. Use a whisk to mix these ingredients together until they are well combined and the mixture is smooth.

Add the large eggs and vanilla extract to the butter-sugar mixture. Beat with the whisk until everything is fully incorporated and the mixture is lightened slightly.

In a separate bowl, whisk together the all-purpose flour, baking powder, and salt. This ensures that the baking powder is evenly distributed throughout the flour.

Gradually add the dry ingredients to the wet ingredients, mixing on low speed or by hand until just combined. Be careful not to overmix the batter, as this can lead to tough blondies.

Fold in the semi-sweet chocolate chips until they are evenly distributed throughout the batter.

Pour the blondie batter into the prepared baking pan and spread it evenly using a spatula.

Bake in the preheated oven for 25-30 minutes, or until the edges of the blondies are golden brown and a toothpick inserted into the center comes out with a few moist crumbs attached. The center should still be slightly gooey.

Remove the pan from the oven and let the blondies cool completely in the pan before cutting them into squares. This will prevent them from crumbling.