Combine the flax and 6 tbsp. warm water in a small bowl, whisk, and set aside for a few minutes.

In a large bowl, beat the butter and sugar until fluffy. Add the flax, and beat until combined.

In a small bowl, combine the flour, baking powder, and salt. Slowly add the flour mixture to the sugar mixture, adding in the milk bit by bit to help everything combine.

Place the batter on a large piece of parchment paper, and fold the paper over the batter. Press the paper down so the batter gets to about 3/4" to 1" thickness, and then put in the fridge for 20-30 minutes.

Heat your oven to 350 degrees.

Begin rolling out the dough to about 1/4" thickness and cut it to your desired shapes.

Place the cookies on your cookie sheet, and bake, 13-15 minutes, until lightly browned.

Cool completely - for at least an hour.

In a medium bowl, beat the sugar and butter together, little by little, adding in the vanilla and almond milk throughout the process to help the icing stay smooth.

Spread the icing on the cooled cookies, and top with sprinkles, if desired.

In order to harden the icing, leave the cookies out for 6-8 hours. Enjoy!