Coat the inside of an 8-inch x 8-inch baking dish with nonstick cooking spray. Set aside.
Melt the butter in a large pot over medium heat. Once melted, add in the marshmallows, and stir constantly until completely melted and smooth.
Pour in the crushed Oreos and stir until completely mixed. Pour the cookie mixture into the prepared pan and use your hands to press it into an even layer gently.
Allow to cool for 5 minutes. Then press cookie cutters into the marshmallow mixture in any shape you like. (I recommend a larger and smaller size cookie cutter to get the most out of the pan.) DO NOT remove the shapes yet.
Once the treats are cooled completely you can take the shapes out of the pan. You may need to use a knife to cut any edges that are partially connected.
Add white chocolate chips and coconut oil into a medium microwave-safe bowl. Heat in 30-second intervals, stirring between each heating, until melted and smooth.
Line a baking sheet with parchment paper. Place a treat on a fork and dip it into the melted white chocolate until completely covered. Allow the excess chocolate to drip off back into the bowl, and them place it onto the baking sheet.
Top the treats with sprinkles while the chocolate is still wet. Let them rest until the chocolate has set up.
Notes
The number of treats this recipe makes will vary based on the size and shape of the cookie cutters.
The Double Stuf, Cakesters, and Fudge Covered Oreo varieties are not recommended for this recipe. The "cookie" texture, filling amount, and extra chocolate change how the ingredients work together to make the treats.