Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper or silicone baking mats.
In a large bowl, beat the softened butter, granulated sugar, and brown sugar with an electric mixer on medium speed for 3–4 minutes until light, fluffy, and pale. Scrape down the sides as needed.
Add eggs one at a time, beating well after each addition, then mix in the vanilla extract and beat on medium for another minute until smooth and glossy.
In a separate bowl, whisk together the flour, cocoa powder, baking soda, and salt until well combined with no lumps.
With the mixer on low, gradually add the dry ingredients to the wet mixture and mix just until no streaks of flour remain — do not overmix. The dough will be thick and slightly sticky.
Roughly chop 15 Oreos and fold them into the dough using a rubber spatula, along with the white chocolate chips if using; reserve the remaining 5 Oreos for topping.
Use a 2-tablespoon cookie scoop to portion dough onto the prepared baking sheets, spacing 2 inches apart, then press 2–3 pieces of reserved Oreo onto the top of each dough ball.
Bake for 11–13 minutes until the edges are set but the centers still look slightly underdone; the cookies will continue to firm up on the hot pan.
Let cookies rest on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely — or enjoy warm straight from the pan.