Line a baking sheet with parchment paper.

Place the Oreos, including the filling, in a food processor and pulse until finely crushed. If you don't have a food processor, place them in a large zip-top bag and crush them with a rolling pin. You should have fine crumbs with minimal chunks. Set aside a tablespoon of dry crumbs to use as toppings later if desired. 

Add the softened cream cheese and vanilla to the Oreo crumbs. Pulse in the food processor until fully combined. The mixture will be wet but hold its form.

Cover the bowl with plastic wrap and refrigerate for about 15 minutes. This will make it easier to roll the mixture into balls.

Using a tablespoonful of the mixture at a time, roll between your hands to form a smooth ball (about 1-inch diameter). Place each ball on the lined baking sheet.

Once all the balls are rolled, place the baking sheet in the freezer for at least 15-20 minutes. Chilling helps the balls hold their shape when dipping in chocolate.

Melt the dark chocolate with the oil in a double boiler over low heat or in short bursts in the microwave, stirring frequently until completely smooth and melted. Avoid overheating to prevent the chocolate from seizing. Repeat for the white chocolate, if using. (If using more than one kind of chocolate, divide the oil as needed.)

Remove the truffles from the freezer. One at a time, place a truffle on the fork and spoon the melted chocolate over the truffle until fully coated, tap off the excess, and gently use a knife to transfer from the fork to the lined sheet pan. 

If desired, sprinkle with toppings before the chocolate is set. If adding a chocolate drizzle, do that after the coating has set.

Once all the truffles are dipped and decorated, allow the chocolate to set at room temperature before serving or storing.