Add melted butter, granulated sugar, and brown sugar to a mixing bowl. Cream together with a hand mixer or in a stand mixer with the paddle attachment until light and fluffy, about 2–3 minutes. Be sure to scrape the sides of the bowl a few times to make sure everything is fully incorporated.
7 tablespoons unsalted butter, ¼ cup granulated white sugar, ¼ cup dark brown sugar
Next, mix in the egg and vanilla extract. Mix until fully combined, but don’t continue to mix. Make sure it’s totally combined with no streaks of egg.
1.5 teaspoons vanilla extract, 1 large egg
Gently fold in the flour, baking soda, and kosher salt until almost all the way combined.
1 cup all purpose flour, ½ teaspoon baking soda, ¾ teaspoon kosher salt
Then add in the semi-sweet chocolate chips, dark chocolate chunks, white chocolate chips, white chocolate chunks, and crushed cookie pieces. Use a rubber spatula to combine, then using a small cookie scoop, make 24 small pieces of cookie dough. Place on a parchment lined baking sheet, and refrigerate for at least 30 minutes.
4 sandwich cookies, ¼ cup dark chocolate chunks, ¼ cup semi-sweet chocolate chips, ¼ cup white chocolate chips, ¼ cup white chocolate bar