• Preheat your oven to 350°F. Line a small baking sheet with parchment paper.
• In a very small bowl, whisk together the flour, cocoa and baking soda. Set aside.
  35 g flour, 2 g cocoa, 1/8 tsp baking soda
• Place the butter and chocolate in a small, microwave safe bowl. Heat in the microwave for 30 seconds. Stir to melt the chocolate, return to the microwave in 10 second intervals if necessary to completely melt the chocolate.
  28 g butter, 20 g chocolate
• Whisk in the sugar and brown sugar until well combined.
  15 g sugar, 17 g brown sugar
• Add the vanilla, salt and egg yolk. Whisk until fully incorporated.
  1/8 tsp vanilla, pinch salt, 1 egg yolk
• Stir in the flour mixture until nearly all of the flour has disappeared into the batter.
• Add the chocolate chips and fold them in until all of the flour has disappeared and the chips are evenly distributed.
  15 g chocolate chips

Cookies:

• If you are making cookies, divide the dough into either 4 or 6 equal mounds on the baking sheet (or use a #40 or #30 cookie scoop). Press additional chocolate chips (or whatever baking chip you prefer, I love to use peanut butter chips here) into the top of the mounds.
• Bake for 8-12 minutes (start with 8 minutes for the 6 smaller cookies, start with 10 minutes for the 4 larger cookies). The edges will be set, the center may still look soft. Allow to cool for about 5 minutes on the baking sheet. Enjoy warm, or let cool completely.

Skillet Cookies:

• If you are making skillet cookies, divide the dough evenly between 2 - 3 1/2 in cast iron skillets, pressing the dough into an even layer. Press additional chocolate chips (or whatever baking chip you prefer, I love to use peanut butter chips here) into the top of the dough.
• Place the skillets on the baking sheet and bake in the pre-heated oven for about 15-18 minutes. The edges will puff up and set, the center will stay soft and gooey (if you don't enjoy underbaked cookies, continue to bake for another 2 or 3 minutes). Allow the skillet cookies to cool for about 5 minutes before topping with a scoop of ice cream and your favorite sundae toppings. Enjoy warm directly from the skillets.