Step 1: Preheat your oven to 350°F (175°C).
Step 2: In a large mixing bowl, cream together the softened butter, brown sugar, and white sugar until light and fluffy (about 2-3 minutes).
Step 3: Add eggs and vanilla extract to the butter-sugar mixture and mix until well combined.
Step 4: In a separate bowl, whisk together flour, cornstarch, baking powder, and salt. Gradually add to wet mixture and mix until just combined.
Step 5: Fold in 3/4 cup of chocolate chips, reserving the rest for topping.
Step 6: Take a spoonful of cookie dough, flatten it, place an Oreo in the center, then encase it with more dough.
Step 7: Place dough balls on a baking sheet lined with parchment paper, spacing them about 2 inches apart. Press reserved chocolate chips on top.
Step 8: Bake for 10-12 minutes until edges are lightly golden. Centers may look underbaked.
Step 9: Allow to cool on the baking sheet for about 5 minutes before transferring to a wire rack.