Begin by placing the Green Candy Melts in a microwave-safe bowl. Heat in the microwave on high for 1 minute, then stir. Continue heating in 15-second intervals, stirring after each, until the melts are fully melted and smooth.

Once the candy melts are smooth, add the sweetened condensed milk and Creme de Menthe to the mixture. Stir vigorously until all the ingredients are completely combined and thick and creamy.

Cover your bowl with a clean kitchen towel or plastic wrap and let the mixture cool at room temperature. Stir every 5 minutes until it reaches a thick, frosting-like consistency—about 20-30 minutes.

Prepare a piping bag fitted with a star tip. Once the fudge has cooled to the right consistency, transfer the mixture to the piping bag. On a parchment-lined baking sheet, carefully pipe the fudge into tree shapes.

Gently top each fudge tree with gold star sprinkles, then add rainbow nonpareils. Allow the trees to set at room temperature until firm before serving.