In a large bowl of a stand mixer, add butter and sugars. Using the paddle attachment, mix on medium high speed until everything is completely mixed and becomes light and fluffy (about 2 minutes).

Add in egg and vanilla. Scrape butter mixture from sides of bowl with spatula. Mix on medium speed until egg and vanilla are completely incorporated into the butter mixture.

In a small bowl, add flour, baking soda and salt. Whisk together. Add flour mixture to butter mixture. Turn your mixer speed to the lowest speed possible (usually it is the stir function) and mix the flour until it is only just barely completely incorporated. Be careful not to overmix or the cookies will be more cakey than chewy.

Add in 1 cup of chocolate chunks. Keep the mixer on the lowest speed and mix the chocolate into the batter until the chunks are mixed in. This should only take a few revolutions.

Refrigerate the dough for at least 1 hr.

When ready to bake, preheat oven to 350°F.  Line 3 large baking sheets with silicone baking mats. Using a cookie scoop, scoop 3 tbsp of dough for each cookie. Space the cookies at least 2 inches away from the edges of the baking sheet and from each other. The cookies do spread a lot so I would not bake more than 4 at a time. You can always do 1-2 for your first batch so you can see how much they spread.

Add remaining chocolate chunks to surface of cookies balls, placing them in sections where the chocolate is sparse. I like to make sure the surface of the ball is studded with chocolate. Keep in mind the cookies will spread quite a bit so even if it seems like you're putting on a lot, it will look more evenly distributed once they spread out. Place two of the cookie sheets in the fridge to chill.

Place remaining baking sheet onto the middle rack in the oven. Bake for about 12 minutes or until edges are light brown and middle is cooked but not quite set. Allow cookies to fully cool on baking sheet before removing. If you remove cookies before they are set, they will break. For even cooking, only bake one sheet of cookies at a time. Baking multiple sheets at a time will likely lead to an uneven heat distribution. When one batch is baking, keep the uncooked batches in the fridge so they stay chilled.