Prep the pan and oven: Heat the oven to 350°F (175°C). Line a 9x13-inch metal baking pan with parchment, leaving overhang for easy lifting. Lightly grease.

Melt the butter: Melt butter and let it cool for 5–10 minutes so it’s warm, not hot. This helps keep the bars thick and not greasy.

Whisk the sugars and butter: In a large bowl, whisk melted butter with brown and granulated sugar until glossy and smooth, about 30 seconds.

Add eggs and vanilla: Whisk in eggs one at a time, then vanilla, until fully combined and slightly thick.

Combine dry ingredients: In a separate bowl, whisk flour, baking soda, and salt. This prevents clumps and ensures even rise.

Mix the dough: Add the dry ingredients to the wet. Stir with a spatula until just combined. Do not overmix.

Fold in chocolate: Stir in chocolate chips (and nuts if using), reserving a small handful to press on top for a bakery look.

Spread and top: Scrape the dough into the pan and spread evenly to the corners. Press in the reserved chips. For extra flavor, sprinkle a pinch of flaky salt.

Bake: Bake 22–28 minutes, until edges are set and golden and the center looks slightly underbaked with a soft jiggle. A toothpick should come out with moist crumbs, not wet batter.

Cool and slice: Cool in the pan on a rack for at least 20–30 minutes to set. Lift out with parchment and cut into bars. For clean edges, cool fully before slicing.