Place the Oreo cookies in a zip-top bag and crush them into small pieces using a rolling pin or the bottom of a glass. You want a mix of fine crumbs and small chunks.
In a medium bowl, combine the vanilla ice cream and crushed Oreos. If the ice cream is too hard, let it sit at room temperature for a few minutes to soften slightly, or add a splash of milk to help blend.
Stir vigorously with a spoon or spatula until the cookies are evenly distributed throughout the ice cream. The mixture should be thick and creamy.
Transfer the mixture to a serving cup or bowl. For an authentic McFlurry texture, you can use a spoon to create a swirled effect.
Serve immediately. Optionally top with extra crushed Oreo or whipped cream.
Tips
For a thicker consistency, use less milk or skip it entirely.
For a more authentic taste, use soft serve ice cream if available.
Customize by adding chocolate syrup or substituting with other cookie flavors.