In a large mixing bowl, combine softened butter, granulated sugar, brown sugar, salt, and vanilla. Beat with an electric mixer for 2–3 minutes until the mixture is light and fluffy.
Add the egg and egg yolk, mixing until the batter is smooth and fully combined.
Add the flour and baking soda. Mix on low speed just until the dough starts to come together; do not overmix.
Use a spatula to gently fold in the chocolate chips and Oreo chunks until evenly distributed.
Cover the bowl and refrigerate for at least 1 hour (or overnight for the best flavor) to prevent the cookies from spreading.
Preheat your oven to 180°C (350°F) and line a tray with parchment paper. Use a 1.5 oz scoop to form even dough balls.
Arrange on the baking sheet and bake for 11–12 minutes. The edges should be golden, but the centers should still look slightly underbaked.
Immediately press extra chocolate chips and Oreo pieces into the warm cookies. Let them rest on the tray for 5 minutes before moving them to a wire rack to cool completely.
Notes
Measure by Weight: For the most consistent results, use a kitchen scale. Too much flour can lead to cakey cookies, while too little will cause them to spread too much.
Don't Overmix: Once you add the flour, mix only until you see no more white streaks. Overmixing develops gluten, which makes the cookies tough rather than chewy.
Roughly Chop the Oreos: Avoid crushing the Oreos into fine crumbs. Leaving large, jagged chunks ensures you get that distinct "cookie-on-cookie" crunch and a better visual look.
The "Cookie Scoot": If your cookies come out of the oven slightly misshapen, place a circular glass or cutter over the warm cookie and gently scoot it in a circular motion to pull the edges into a perfect circle.