1-First Step: Preheat and Prep the Pan Preheat your oven to 350°F. Fully line an 8×8-inch baking pan with parchment paper, letting it overhang two sides for easy removal. This prevents sticking and makes cutting clean. Grease lightly if desired. Mise en place: measure all ingredients for smooth sailing.

2-Second Step: Mix the Dry Ingredients In a medium bowl, whisk together 2¼ cups all-purpose flour (270g), 1 tablespoon cornstarch, 1 teaspoon baking soda, and 1 teaspoon salt. Set aside. This combo ensures chewy chocolate chip cookie bars with soft centers and structure.

3-Third Step: Combine Wet Ingredients In a large bowl, mix ¾ cup melted and slightly cooled unsalted butter (170g) with 1 cup packed light brown sugar (220g) and ⅔ cup granulated sugar (133g). Whisk for 30 seconds until thick and smooth. Add 2 room-temperature large eggs and 1 tablespoon vanilla extract. Whisk 1 full minute for emulsion. Vegan? Use flax eggs here.

4-Fourth Step: Form the Dough Add dry mix to wet. Stir with a spatula until nearly combined, avoiding overmixing for tenderness. Fold in most of the 2 cups semi-sweet chocolate chips (360g total, reserve ¼ cup). The dough will be thick. For gluten-free, ensure your flour blend has xanthan gum.

5-Fifth Step: Spread and Top Transfer dough to prepared pan. Spread evenly with a spatula, keeping some top texture for rustic look. Sprinkle reserved chocolate chips on top. This creates melty pools and shine.

6-Sixth Step: Bake to Perfection Bake at 350°F for about 55 minutes. Edges turn golden, center sets a toothpick comes out with moist crumbs. For gooier thick chocolate chip cookie bars, check at 45 minutes. Cool in pan 1 hour on a rack before lifting out.

7-Final Step: Cool, Cut, and Serve Lift using parchment handles. Cool fully, then cut into 16 squares. Pair with milk or coffee. Store as noted below. These steps yield consistent cookie bar recipe success.