Start by lining a large sheet pan with parchment paper or a silicone baking mat. This will help prevent the cookies from sticking and make for easy cleanup.
For the Christmas Trees, combine white chocolate melting wafers and a small amount of vegetable oil in a microwave-safe bowl. Microwave in bursts of 25 seconds, stirring in between, until the chocolate is fully melted and smooth.
Dip the bottom half of one Oreo into the melted white chocolate, allowing any excess to drip off, and place it on the prepared sheet pan to set. Repeat this process for the remaining cookies.
Next, melt the green candy melts with a touch of oil until smooth. Transfer the melted chocolate into a resealable plastic bag, seal it tightly, and cut off a small tip.
Using the green candy melts, pipe a zig-zag shape onto each Oreo to create the outline of a tree. Quickly sprinkle with nonpareil sprinkles and finish with a gold star sprinkle on top, along with a chocolate sprinkle to resemble a trunk.
Now, let's create the Melted Snowmen! Use the remaining white chocolate and repeat the melting process. Use a small amount of melted chocolate to attach a Reese's mini to the top of the Oreo.
Dip a fork into the melted chocolate, then place the Oreo right side up on the fork. Spoon melted chocolate over the cookie to coat it evenly, and tap gently to remove excess chocolate. Transfer the coated Oreo back to the prepared sheet pan.
Quickly attach two mini M&M’s for buttons and an orange jimmie sprinkle for the nose before the chocolate hardens. For the eyes and arms, melt milk chocolate and pipe onto the cookie.
For Rudolph, melt more milk chocolate and follow a similar process as with the snowmen. Dip the Oreo, place it on the sheet pan, and attach two edible eyes and a red mini M&M for the nose. Use melted chocolate to pipe on antlers.
Finally, for the Ornaments, repeat the melting process with white chocolate. Dip the Oreo and place it on the sheet pan. Attach a mini Reese's at the top edge and decorate it with sprinkles or mini M&M’s to resemble a festive ornament.
Allow all cookies to set at room temperature before serving or packaging. Enjoy your festive creations!