Preheat your oven to 350°F (175°C) and position racks in the upper and lower thirds of the oven. Line four baking sheets with parchment paper.

In a small bowl, whisk together the flour, baking soda, and salt. Set aside.

In a medium bowl, beat the softened butter with an electric mixer for about 30 seconds until creamy. Add the brown sugar and white sugar, and beat until the mixture is light and fluffy, about 1-2 minutes.

Mix in the egg, egg yolk, and vanilla extract, ensuring everything is well combined.

Gradually incorporate the flour mixture into the wet ingredients. Stir just until combined—don’t overmix. Fold in the mini chocolate chips.

Divide the dough into four portions. Wrap each in plastic wrap and chill for at least 1 1/2 hours or up to 24 hours.

When ready to bake, roll one dough portion into a rope about 1/2 inch in diameter. Cut into 1/2-inch pieces, using a bench scraper for neat cuts. Arrange the pieces on the prepared baking sheets.

Place two sheets in the oven and bake for 8-9 minutes, rotating the pans halfway through. The cookies should be golden brown. Let them cool completely on the baking sheets before serving.