- Preheat the oven to 350°F.
- Grease and flour a 13x9 pan.
- Prepare, bake and cool cake following package directions.
- For decorator frosting: combine confectioners sugar, shortening, water, non-dairy creamer, vanilla and salt in large bowl.
- Beat at medium speed with electric mixer for 3 minutes.
- Beat at high speed for 5 minutes.
- Add more confectioners sugar to thicken or more water to thin as needed.
- Reserve 1 cup frosting.
- Tint remaining frosting with green food coloring.
- Cut cooled cake diagonally and invert one piece so that the cake takes on a tree shape with a wide base.
- Spread green frosting over cake.
- Decorate tree with reserved white frosting and peppermint candies.
- Make trunk from pretzel rods.
- Roll out large gumdrop and cut with star cookie cutter.
- Top tree with gumdrop star.