Melt the unsalted butter in a shallow, light-colored pan over medium-low heat. Cook, swirling the pan often, for 5-7 minutes. At first the butter will foam up and get bubbly, but after a few minutes, you will start to see small brown bits on the bottom of the pan. Once the butter is golden-brown and smells nutty, immediately remove the butter from the heat and pour it into a large heat-proof mixing bowl. Cool the brown butter until it's room temperature, about 10-15 minutes.

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

Add the dark brown sugar and white sugar to the cooled brown butter. Using a hand mixer, beat the butter and sugars together until it's combined, about 1-2 minutes. The mixture will be a bit sandy. Mix the egg and vanilla extract into the butter-sugar mixture until it's very smooth.

Add the flour mixture to the butter-sugar mixture and beat just until the dough comes together. A few streaks of flour are ok. Fold the mini chocolate chips into the dough, just until combined. Don't over-mix!

Using a #100 scoop or teaspoon, scoop the dough into balls and roll them until smooth. Place the tiny cookie dough balls on a parchment lined sheet pan and chill, covered, for 1-2 hours or overnight.

While the cookie dough balls are chilling, preheat the oven to 350°F (177°C). Line 2 sheet pans with parchment paper.

Place the cookie dough balls on the prepared sheet pans 2-inches apart (15-16 cookies per pan). Bake for about 6 minutes, just until the edges of the cookies are set and the centers are still a bit underdone.

Let the cookies cool on the sheet pan for about 5 minutes. Then, transfer them to a wire rack to cool completely. Repeat the above steps with the rest of the cookie dough balls. Enjoy!