Design Eat Repeat

13 If you made this recipe prior to 3/28/22, I’ve since made a few tweaks as some readers were having trouble with them being too cakey. See notes section below for what I changed!
0 Preheat oven to 350°F.
1 Place ½ cup of chocolate chips on a cutting board and use a knife to chop into small pieces. Set aside.
2 In a medium-sized microwave-safe bowl, melt the unsalted butter (¾ cup, i.e. 1 ½ sticks) for 20-30 seconds until JUST melted. (If your butter is steaming, let it cool down for a few minutes. Butter that is too hot can result in greasy bars and/or will cause the eggs to cook.)
3 Add in granulated sugar (½ cup) and light brown sugar (¾ cup) and use a spatula to stir until combined (* do not use a mixer!). Add in eggs (1 whole + 1 extra egg yolk) and vanilla extract (2 teaspoons). Mix until combined.
11 Stir in baking soda (1 teaspoon), baking powder (¼ teaspoon), and salt (½ teaspoon). Add in all-purpose flour (2 cups), ½ cup whole chocolate chips, and the ½ cup of chopped chocolate chips. Mix until all the flour disappears into the dough. Immediately proceed to the next step.
4 Press dough into a greased or parchment-lined metal 9x13" pan until smooth. Sprinkle the remaining ½ cup whole chocolate chips on top and gently press each one into the dough.
6 Bake at 350°F for 16-18 minutes until edges and top are lightly golden brown. Do not overbake or your chocolate chip cookie bars will not be soft. You want the cookie bars to be lightly brown on the top and look slightly underbaked (my oven was perfect at 16 minutes). Remove from oven and place entire pan on a cooling rack. 
12 Allow the cookie bars to cool completely before removing from pan. Slice into 24 squares, then enjoy! To keep fresh, cover pan with saran wrap or place bars in airtight continer for up to 3 days (after that they start to dry out). See notes below for freezing tips.