Prepare the Oven and Baking Sheets: Preheat the oven to 350°F. Line 2 baking sheets with parchment paper and set them aside.
Cream the Butter and Sugars: Place the softened butter, packed light brown sugar, and granulated sugar in a large bowl. Using an electric mixer on medium speed, beat for about 3 minutes, until the mixture is fluffy. Scrape down the sides of the bowl as needed. Add the Eggs and Vanilla: Beat in the room-temperature egg, egg yolk, and vanilla extract until the mixture is thoroughly combined.
Combine the Dry Ingredients: In a separate bowl, whisk together the all-purpose flour, baking soda, and salt until evenly mixed.
Incorporate the Flour Mixture: Add the dry ingredients to the butter mixture. Beat on low speed just until the flour is almost completely incorporated, taking care not to overmix.
Add the Chocolate Chips: Gently fold the semisweet chocolate chips into the dough until they are evenly distributed.
Portion the Dough: Using a 1.5-tablespoon cookie scoop, portion the dough into mounds on the prepared baking sheets. Arrange them about 2 inches apart to allow room for spreading.
Bake the Cookies: Bake at 350°F for 10–12 minutes, or until the edges are lightly browned while the centers still look just underdone.
Cool on the Baking Sheets: Leave the cookies on the baking sheets for 10 minutes after removing them from the oven.
Finish Cooling: Carefully transfer the cookies to a wire rack and allow them to cool completely.
