I have not made one but I have looked at some and I think they use an upside down ice cream cone and frost it green(the flat bottom one I believe).
Sandra
I made one a few years ago...the one where you bake two bundts and stack them with the bottoms together! The hole part just stayed empty and then you put and upside down ice cream cone (the flat bottom ones) in the hole and attach with icing so you don't even see the hole.
I made one a few years ago. I baked a "stem"cake in a clean soup can. I just took the label off, washed the can well, and greased it. I filled it about 3/4 of the way full. It came out well. Wish I had a picture. 
I make this cake every Halloween....bake two bundt cakes, and turn the first one upside down. Frost (or fill) the top, then place the other cake rightside up. Stick a ding dong in the upper bundt cake to fill the hole, then frost over it. Very simple, very easy!
I did mine with Pound cake and yes and upside down Ice cream cone that I covered. It was a little challenging but fun. Learned a lot.
OP, yes! it totally works. I did it this past Thanksgiving. Make two bundt cakes and put them on top of each other to make the sphere. For the middle, I actually made extra batter and made cupcakes with that. Then I used a circle cutter to cut circles of the cupcakes and stacked those in the middle. The stem can be made with fondant or gum paste or mix. The little swirly things out of the pumpkin you can do with the mix just wrap around a pencil and let it freeze to harden. Good luck!
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