Preheat your oven to 375° Fahrenheit (190° Celsius). Line a cookie sheet with parchment paper and set it aside.

In a medium saucepan, melt 1 stick of butter over medium heat, stirring constantly until golden brown with little brown bits at the bottom. Pour into a large bowl and immediately stir in the remaining ½ stick of cold butter cubes to cool the mixture.

In a small bowl, whisk together 1 ½ cups of flour, ¾ teaspoon of baking soda, and ¾ teaspoon of kosher salt.

Add 1 cup of light brown sugar and ¼ cup of granulated sugar to the cooled butter mixture, whisking until smooth.

Whisk in 1 large egg, 2 large egg yolks, and 2 teaspoons of vanilla extract until the mixture is creamy.

Slowly fold the flour mixture into the wet ingredients using a spatula, mixing until no dry spots remain.

Stir in 1 cup of semi-sweet chocolate morsels and ¾ cup of chopped walnuts until evenly distributed.

Cover and chill the dough in the refrigerator for 30 minutes.

Scoop the chilled dough into 30 evenly sized balls, about 1-2 tablespoons each, and place them on the prepared baking sheet.

Press the remaining ¼ cup of chocolate chips and ¼ cup of chopped walnuts on top of each dough ball. Bake for 10 minutes, tapping the tray on the counter at the 6-minute mark to flatten slightly.

Sprinkle flaky sea salt on the cookies as soon as they come out of the oven. Let them cool on the baking sheet for 10 minutes before transferring to a cooling rack.