Place the oreo cookies in a blender or food processor and crush them for about 30 seconds until a very fine powder is obtained. Set aside 2 tablespoons of cookies to decorate at the end.
Add in the cream cheese and blend for another 20 seconds until a smooth and homogeneous mass is obtained.
Form small balls of 1 1/2 tablespoons of dough and place them on a large tray lined with baking paper. There should be approximately 24 truffles. Place the tray with the truffles in the refrigerator for at least 30 minutes.
Separately, 5 minutes before removing the truffles from the refrigerator, place the chocolate chips with the oil or butter in a microwave-safe bowl and melt in the microwave for 30-second intervals, i.e., put them in the microwave for 30 seconds and take them out and mix a little with a fork. Repeat the process until the chocolate is completely melted (this prevents it from burning).
Once the truffles are cold, remove them from the refrigerator to cover them with the chocolate. To do this, with the help of a fork, take each truffle and place it in the dish with the melted chocolate, turning it so that it is covered on all sides. Once well coated, shake it a little to remove the excess chocolate, place it back on the tray and immediately decorate with some graham crackers, sprinkles or with more oreo cookie dust if desired (the leftover from the begining).
Repeat the previous step with the rest of the truffles and, once they are all ready, put them back in the refrigerator for at least another 30 minutes. That's it!