In a large mixing bowl, cream sugar and butter.

Add in egg and vanilla, and mix until incorporated.

In a medium bowl, combine flour, baking powder, and salt.

Mix into sugar mixture until well-combined.

Chill dough for 1-2 hours.

On a generously floured surface, roll out dough and use cookie cutters to cut shapes.

Bake at 400 degrees for 7-9 minutes on an ungreased baking sheet. Cool completely.

Combine all ingredients in a small mixing bowl, adjusting water and powdered sugar as needed to achieve desired consistency. Mix until fluffy.

Fill a piping bag fitted with a #3 tip with buttercream frosting, and set aside.

In a medium bowl, combine all ingredients and whisk until smooth. Consistency should be that of a thick syrup, similar to molasses. Adjust water and corn syrup accordingly.

Separate royal icing into individual bowls, 1 for each color you'll be using, and mix in food coloring until it reaches desired color.

Using the buttercream frosting in the piping bag, pipe an outline around the border of the cookie. Allow to set up for about 10-15 minutes before flooding.

When ready to flood, use extra piping bags or a small spoon to drizzle different colors of royal icing onto each cookie.

Use a toothpick to drag icing to the edges, without allowing it to spill over.

Swirl with toothpick until you reach a desired pattern!

Allow to dry for 2-4 hours.