¾ cup unsalted butter (not margarine) You will be melting this

¾ cup light brown sugar

½ cup granulated sugar

1 large egg + 1 yolk (i.e. 1 whole egg + 1 extra egg yolk)

2 teaspoons vanilla extract

¾ teaspoon baking soda

¾ teaspoon salt

¾ cup unsweetened cocoa powder I use Hershey's

1 ½ cups all-purpose flour

1 ½ cups semi-sweet chocolate chips (divided, 1 ¼ cups in dough + ¼ cup sprinkled on top)

Preheat oven to 350°F.

In a medium-sized microwave-safe bowl, melt unsalted butter (¾ cup, i.e. 1 ½ sticks) for 30-60 seconds until fully 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.

Add in light brown sugar (¾ cup) and granulated sugar (½ cup) and use a spatula to stir until combined. Stir in 1 whole egg, 1 extra egg yolk and vanilla extract (2 teaspoons). Mix until combined.

Stir in baking soda (¾ teaspoon) and salt (¾ teaspoon).

Add in unsweetened cocoa powder (¾ cup) and all-purpose flour (1 ½ cups). Before all the flour disappears, add in 1 ¼ cups of chocolate chips. Mix until all the flour disappears into the dough. Immediately proceed to next step.

Press dough into a greased or parchment-lined metal 9x13" pan until smooth. Sprinkle the remaining ¼ cup chocolate chips on top and gently press each one into the dough.

Bake at 350°F for 14-16 minutes, or until center no longer looks wet. Do not overbake or the bars will not be soft & may taste bitter. Remove from oven and place entire pan on a cooling rack. If desired, sprinkle with flaky sea salt.

Allow the cookie bars to cool completely before removing from pan. Slice into 12-24 squares, then enjoy! To keep fresh, cover pan with saran wrap or place bars in airtight continer for up to 2-3 days (best within 2 days or they start to dry out). See notes below for freezing tips.