A plain or chocolate dipped ice cream cone makes a great stem. THis is a great cake, kids adore. I have been using it for about 5 years now. :) I actually did see it in Family Fun magazine.
I made myself a blue pumpkin cake for my birthday with this but I didn't turn it into a jack o latern, I have to admit. I tried putting a cupcake on top for the stem and decided it would have been too thick of a stem so I used a Cadbury's Flake Bar, which looks very stem-like! This is a really fun idea for a cake and it's really really big!