1. First melt the butter. I usually do this in the microwave and I melt it just enough so that it is still thick and creamy-looking. Take it out when there is still some solid butter left and then stir to let the residual heat melt it. The butter should be cool but fluid. Combine this melted butter with brown sugar, granulated sugar and vanilla in a small bowl and mix until smooth and creamy.

2. Mix in egg yolk until evenly combined. Sprinkle over the flour and then sprinkle over the baking soda and salt. Fold it in gently until incorporated, then add chocolate chunks and fold them in. Cover the bowl and set it aside while you preheat the oven. This rest time will improve the texture of the cookies.

3. Preheat oven to 350°F. Line a large cookie sheet with parchment paper.

4. Divide dough into 7 equal portions and roll into smooth balls. Place them onto prepared baking sheet spacing them at least 2 inches apart. Flatten slightly with the palm of your hand.

5. Bake for 8-10 minutes until golden around the edges and puffed. They should still be soft in the middle. Transfer to a wire rack to finish cooling, but definitely eat a few while they are warm!