Line a 9x9-inch baking dish with parchment paper, ensuring to leave an overhang for easy lifting later.

In a medium saucepan set over low heat, combine white chocolate chips and sweetened condensed milk. Stir continuously for about 5–7 minutes until smooth.

Remove from heat and stir in marshmallow cream and vanilla extract until well combined.

Gently fold in the chopped chocolate sandwich cookies, reserving a few for topping.

Spread the fudge mixture into the prepared pan, smoothing the top, and sprinkle reserved cookie pieces over the surface.

Refrigerate for at least 3 hours until firm, then cut into squares.