Line a medium sized baking sheet or cutting board with parchment paper and set aside.
In the bowl of a large food processor, add in Oreos (WITH the filling). Grind until the Oreos become very fine and crumbly.
Add your melted butter and 2 tablespoons of milk to the Oreo crumbs. Pulse the mixture until it's well moistened and sticks together without crumbling. If needed, pulse in more milk, 1 tablespoon at a time, until the mixture comes together.
Scoop out 1 tablespoon sized portions and roll between your hands into a smooth ball. Arrange on your parchment lined baking sheet.
If you find the mixture is too crumbly to roll, blend in some more milk and try again. If you accidentally add too much milk and the mixture is too sticky to roll, scoop out the portions and drop them onto your baking sheet then chill in the freezer for 5-10 minutes or until firm enough to roll smoothly.
Place the Oreo balls in the freezer to chill for at least 15 minutes or until solid before dipping in chocolate.
Melt chocolate in your microwave or on the stove over a double boiler.
To melt in your microwave, place the chopped chocolate in a microwave safe bowl. Heat in your microwave in 10 second bursts, pausing after each one to stir, until melted and smooth.
To melt on your stovetop, place a pot filled with 1 inch of water over high heat until the water starts steaming but not boiling. Reduce heat to low to maintain a very light simmer. Place chocolate in a heat safe bowl that's large enough to fit into your pot without the bottom of the bowl touching the surface of the water. Warm the chocolate, stirring frequently, until melted.
If using, mix oil into the melted chocolate and set aside for 5 minutes to cool slightly. If the chocolate is too hot, it can melt the Oreo balls!
Drop one Oreo ball into the melted chocolate and quickly toss to coat. Use a fork or chocolate dipping utensil to lift the ball up and gently shake over the bowl to allow the excess chocolate to drip off.
Place the chocolate dipped Oreo ball back onto your parchment lined baking sheet. Leave the truffles plain or top with some flaky sea salt or crushed Oreo crumbs while the chocolate is still wet. You can also drizzle the tops with white chocolate after the coating has firmed up. Repeat with the remaining truffles.
Chill the Oreo balls in the fridge or freezer until the outside chocolate layer is set. Keep stored in the fridge until ready to serve!