Preheat the oven to 350°F.
In the bowl of a stand mixer or with an electric hand mixer, combine the butter and powdered sugar until smooth.
Add in the eggs and cake batter flavor, mixing until mostly combined.
Add the flour, baking powder and salt. Begin to mix and add up to the 3 tsp of water to bring the dough together, the dough should be soft and easy to work with.
Roll the dough out until approx 1/2 inch thick and use a christmas tree cookie cutter to cut the dough.
Arrange on a silicone or parchment lined cookie sheet. Bake at 350°F for 7-9 minutes or until the cookies are matte looking on top and have puffed up.
Allow the cookies to cool completely and then make the glaze.
To make the glaze, whisk together the warm water, corn syrup and vanilla. Once the corn syrup is dissolved, add in enough white food coloring to make the water mixture completely white.
Whisk in the sifted powdered sugar, whisking until smooth.
Feel free to add a tiny bit more water to get a smooth consistency that drizzles and melts back into itself within about 5 seconds.
Remove and set aside 2 tbsp of the icing.
Warm the white icing in the microwave and then pour and spread onto each cookie. Top with the green sprinkles before the icing has set.
Once all of the cookies have been iced, dye the set aside icing red using red gel food coloring.
Transfer the icing into either a piping bag or a small zip top bag and snip the corner.
Moving from left to right and then back again, drizzle the red icing onto each christmas tree.
Allow the cookies to set completely before serving.
Store in an airtight container for up to 3 days at room temperature, enjoy!