To brown the butter - place the butter in a medium saucepan with a light-colored bottom. Cook over medium heat, stirring often. It will start to foam, then milk solids will form on the bottom of the pan, and the butter will change to golden brown. As soon as that happens, quickly pour the butter into a large bowl, using a rubber spatula to scrape out every drop. Let cool for 10-15 minutes.

Add the white sugar and brown sugar. Whisk until smooth. Add the egg, yolk, vanilla, and sour cream. Whisk again.

In a small bowl, whisk together the flour, soda, and salt. Add to the wet ingredients with 1 1/2 cups of the chocolate chips. Stir until no streaks of flour remain.

Scoop 2 tablespoons of dough and roll into a ball. Repeat with the remaining dough. Press balls down slightly with your palm, then place them on a cookie sheet. Cover and chill for 2 hours.

Remove cookie dough balls from the fridge. Preheat your oven to 350°. Line a cookie sheet with parchment or silicone liner. Place dough balls at least 2 inches apart.

Bake at 350 degrees for 9-10 minutes. Press a few of the remaining chocolate chips into the top of each cookie.

Let cookies cool on the pan for 3-4 minutes, then transfer to cooling racks to cool completely.