Whether you're baking themed treats for a “Polar Express” Christmas party or just have a house full of locomotive lovers, learning how to make a Christmas cookie train makes for a fun, festive and tasty way to celebrate the holiday. First, decide whether you want to make a two-dimensional outline train, or go all-out and construct a three-dimensional, freestanding gingerbread train. Either way, you'll “wow” your audience with a homemade marvel that looks (almost) too good to eat.
Start with a half-pound of basic cookie dough like sugar or peanut butter, and add another 1/4 cup of flour to make it stiffer and drier. Roll it out and cut as many rectangles as you want for the cars and engine, plus smaller rectangles and a triangle to make the engine's cab, smokestack and cowcatcher. Bake the pieces according to the recipe directions. After cooling, assemble the cookie train on a long, foil-covered board, using a small amount of frosting to stick the cars into place. Frost all the cars using any frosting colors you like, piping around the edges with a contrasting color. Add details like windows and use assorted candies and cookies to create passengers and cargo. For example, populate a circus car with animal crackers, or make people with M & M faces, adding tiny frosting dots for features. Use round peppermint candies for wheels and M & Ms for the couplings between cars.
The two secrets to success in constructing your 3-D cookie train are the special icing that glues the pieces together, and the stacks of glued-together graham crackers hidden inside each car to give it support. Whip up a quick batch of icing glue with 4 egg whites, 6 cups of powdered sugar and 1/2 teaspoon cream of tartar. Next, plan the size, shape and number of cars, and make cardboard templates for the side, back, front and roof panels. Make a circle template for the wheels. Use these templates to cut out the components of your 3-D Christmas cookie train. Use a dough recipe designed for building gingerbread houses and roll it out flat to cut out your train parts. Bake the pieces according to the recipe, then assemble the cars and decorate them with festive candies like gumdrops, M & Ms, licorice twists and peppermints.