I made the most simple and fun Christmas Tree Cake with my kids this past holiday season. I was given this fun green Christmas Cake pan from Wilton. It was really easy. The kids wanted a chocolate cake, so we mixed up a regular chocolate cake mix. I sprayed the pan a little extra so the cake would pop out easily. I cooked the cake and let it cool in the pan for about 15-20 minutes. After this, I placed a cooling rack on the pan and then flipped it over. Again I waited a couple of minutes and then I pulled up the pan and the cake slid out perfectly. I then waited until the cake was completely cooled before icing the cake.
I used regular chocolate icing for the trunk of the tree and applied it using a regular spatula from Wilton. Then for the green icing I have a special tip #2010 (Wilton) that has three tips in one. It looks similar to tip #18 or Tip #21, it is just three times as quick. To make the green icing I used a vanilla icing and dyed it the color Leaf Green (Wilton).
The best part was when my kids helped covering the cake with Smarties. My kids love candy on cakes and it really looks fantastic. Then, when the other kids at the holiday party saw the cake their eyes lit up and smiles appeared on all their faces.