Serves about 40.
Spray 12 in. round pan with vegetable pan spray, or line with plastic wrap. Following recipe instructions, melt butter and marshmallows; stir in green icing color (tint slightly darker than how you want your finished treat to look). Press half of mixture into prepared pan. Let stand 15-20 minutes until set. Remove from pan to foil wrapped cake circle. Repeat with remaining cereal mixture. (If mixture has firmed too much, microwave 10-30 seconds to soften.) Stack onto layer on cake circle. Insert dowel rods where tree will sit.
Spray loaf pan with vegetable pan spray, or line with plastic wrap. Press chocolate rice cereal crispy treat mixture into pan. Let stand until slightly firm to touch. Remove from pan and using hands, shape into tree trunk with roots. (If mixture has firmed too much, microwave 10-30 seconds to soften.) Let stand until firm.
Melt assorted Candy Melts candy following package instructions. Pipe color details in Mint Disc molds using melted candy in parchment bag or disposable decorating bag with small hole cut in tip, or paint details using Decorator Brush. Refrigerate until firm. Fill remainder of mold with melted candy. Refrigerate until firm; unmold. Or, fill molds with one color of melted candy only. Refrigerate until firm; unmold.
Place cereal "tree" on base, securing with melted candy. Insert pretzel rod "branches" into "tree", securing with melted candy; press cereal mixture around branch, if needed.
Attach prepared candy and icing decorations to branches using royal icing or melted candy. Attach face icing decorations.
Pipe tip #47 white buttercream fence around sides of round treat. Pipe tip #233 green buttercream grass tufts around cake top and at bottom border. Attach flower and butterfly icing decorations.