Line a rimmed baking sheet with parchment paper. Place the Oreos on the prepared baking sheet.

In a small microwave-safe bowl, melt the white chocolate or white candy melts according to the package directions until smooth.

Working with one Oreo at a time, dip the bottom half of the Oreo into the white chocolate, then lay on the prepared baking sheet to harden (about 15 minutes).

When the white chocolate is set, melt the green candy melts in a small microwave-safe bowl, according to the package directions until smooth.

Add the melted green candy to a piping bag fitted with a size 1 or 2 piping tip.

Using a zig-zag motion, pipe lines into the shape of an abstract tree, then add decorations. (Only do 1 or 2 Oreos at a time because the candy sets up quickly, you want to make sure your decorations will stick.)

Allow cookies to set completely before serving or packaging. Store leftovers in an airtight container at room temperature for up to 2 weeks. Oreos freeze well, up to 2 months, but Oreos will lose a bit of their crunch.