Christmas Wreaths

Bahan-bahan (20 porsi)

• 4 cups cornflakes cereal, (divided)
• 1/2 cup (1 stick) unsalted butter
• 30 large marshmallows, (from 1 (12-oz/340 g) bag)
• ¼ teaspoons salt
• 1½ teaspoons green food coloring
• 1 teaspoon vanilla extract
• Red decorating icing with a plain piping tip, (for berries (see note))
• Confectioners' sugar, (for snow (optional))