Begin by placing the green candy melts in a large microwave-safe bowl. Microwave on high for 1 minute, then remove and stir. Continue heating in 15-second bursts at 50% power until fully melted and smooth.

Once the candy melts are perfectly melted, stir in the sweetened condensed milk and creme de menthe. Fold the mixture gently until fully blended.

Cover the bowl with plastic wrap and let the fudge cool at room temperature, stirring every 5 minutes until thickened to a frosting-like consistency.

Once thickened, fit a piping bag with a star nozzle and fill it with the fudge mixture. Pipe the fudge into tree shapes on a lined baking sheet.

While the fudge is still soft, add a gold star sprinkle to the top of each tree, followed by a sprinkle of rainbow nonpareils.

Allow the decorated fudge trees to set at room temperature for about 30-60 minutes until firm.