In a medium bowl, whisk together the flour, cocoa powder, baking powder, and salt. Set aside.

In a large bowl, beat the butter until smooth and creamy. Add the sugar and beat until light and fluffy, about 2 minutes. Beat in the egg and vanilla, scraping the sides of the bowl as needed.

Gradually add the flour mixture to the wet ingredients, beating on low until combined.

Divide the dough in half, shape into two disks, and wrap in plastic wrap.

Place dough in the refrigerator to chill for about 1 hour.

After the dough has chilled, remove from the refrigerator and preheat the oven to 350 F. Line two baking sheets with parchment paper.

Place one disk of dough between two sheets of parchment paper and roll out to about ½ inch thickness.

Cut dough out using cutters, paper templates, or a mix of both. To make two train cars and one engine, you will need 9 rectangles, 6 squares, 5 front train pieces, 11 1-inch circles, and 2 ½ inch circles. Cut some extras too, in case one breaks.

Place cut cookies onto prepared baking sheets and bake for 10 minutes. Cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.

In a medium bowl, whisk together the powdered sugar and meringue powder.

Add the water and orange extract and beat on low speed until combined.

Beat on high speed until glossy and icing forms stiff peaks.

Transfer a couple scoops of icing to a separate bowl and stir in desired amount of red food coloring.

Transfer both bowls of icing to piping bags fitted with small or medium round piping tips.

Once the cookies have cooled completely, start by assembling the carriages. Take three rectangle cookies and place one flat on your working surface. Pipe a line of icing on one of the long edges of each of the other rectangle cookies. Press the edges with the icing onto the long edges of the flat cookie bottom. Pipe icing around the bottom and sides of the short sides of the carriage. Place one square cookie on each side of the carriage. Repeat all steps to make a second carriage. Set aside to let the icing set completely.

Assemble the engine car. Place a square cookie flat on your working surface. Pipe two lines of icing along the front and back edges of the cookie. Place two rectangle cookies short edges down into the icing. Pipe icing around three edges of two square cookies. Press one cookie onto each side of the engine car, to make a window. Set aside to let the icing set completely.

Assemble the engine by taking 4 engine shape cookies and piping icing on the front of three of the cookies. Stack them on top of each other and set aside to let the icing completely. Once set, pipe icing on the back of the last cookie and press into one of the long rectangle cookies that make up the engine car. Take the leftover engine front cookie and cut the bottom off of it. Pipe around the top and back of the bottom piece and attach to the bottom front of the engine.

Assemble the smoke stack by taking 3 small circle cookies and piping icing on the front of two of them. Stack them on top of each other and pipe a swirl of icing on the top cookie. Set aside.

Add the wheels to the carriages by piping some frosting on 8 small circle cookies. Place two on each side of the carriages. Pipe some frosting on two of the medium round cookies. Place one on each side of the engine car. Pipe some icing on the bottom of the smoke stack cookies and place on top of the engine cookies.

Decorate one of the leftover rectangle cookies as desired and place on top of the engine car. If you don’t want to put anything into that car, you can secure the cookie using a bit of icing.

Decorate the rest of the carriages as desired, using the red and white icing. Let icing set completely before moving.