Cut out rice krispies with a tree cookie cutter. Place back on parchment paper.
Melt green candy melts as directed on the package and add to a piping bag. Pipe around the edges and across point to point of the Christmas tree.
If you can't get Green Candy Melts, you can substitute them with white chocolate buttons and green gel food colouring.
Rather than using a pan and heating on the stove, you could do this in a microwave in a microwave-safe bowl.