Preheat your oven to 350°F (175°C) and line two cookie sheets with parchment paper.

Melt unsalted butter, then mix with brown sugar and white sugar until smooth. Add egg, egg yolk, and vanilla extract, and blend until creamy.

Gradually add flour, baking powder, baking soda, and kosher salt to wet mixture, stirring until the dough is soft and cohesive.

Fold in mini semi-sweet chocolate chips until evenly distributed throughout the dough.

Scoop out dough with a teaspoon, roll into balls, and place six per row on prepared sheets with 1.5 inches spacing.

Bake in the oven for about 8 minutes until lightly golden. Watch closely to ensure centers remain chewy.

Cool on baking sheets for 3 minutes, then transfer to a wire rack to cool completely.