Keep the butter at room temperature. Make sure it is fully softened before beginning.
Preheat the oven to 350 degrees F.
Mix together the flax meal and water and set aside for 15 minutes to make a "flax egg" before starting.
In the meantime, mix together the flour, baking powder and salt with a whisk in a bowl.
Once the flax egg is ready, in a separate bowl use an electric mixer to cream together the butter and sugar for 2 minutes. Once creamed, add in the flaxmeal with water mixture and vanilla.
Add the wet ingredients to the dry using an electric mixer.
Once a dough begins to form, you can shape it with your hands or use a mixer to get the remaining chunks combined. When the dough comes together, roll it out onto a floured surface and begin shaping the cookies with a cookie cutter.
Using a silicon mat or parchment paper, lay the cookies on a baking tray.
Once the oven is ready, bake the cookies for 7 minutes on the middle rack.
While the cookies bake, use an electric mixer to cream together the icing ingredients until the icing forms peaks.
By the time the icing is ready, the cookies should be just about done. Remove them from the oven after 7 minutes and let them cool for an hour. Do not try to remove them from the baking tray until they are fully cooled, or they will break apart!
Once they are completely cooled down, frost the cookies and throw some sprinkles on there!
Eat them fresh or store them at room temperature. See storage notes below.