Pre-heat oven to 350*F. (If your oven runs hot and browns cookies quickly like my newer oven, try 325*F and bake the cookies for an extra few minutes).
In a large bowl, beat together the butter and sweetener until light and fluffy. Add your egg and extracts and beat once more until combined.
In another bowl, whisk together all of your dry ingredients including; almond flour, coconut flour, arrowroot starch, xanthan gum and salt.
Pour the dry ingredients into the wet and stir well until the dough becomes thick and everything is incorporated together.
Refrigerate your dough for 10-15 min prior to rolling (this is optional, I skip it often but it can be helpful if you find it difficult to cut shapes without tearing your cookie dough).
Line cookie sheets with parchment paper and set aside.
Take two large pieces of parchment paper, grease them lightly with oil or butter and then place your dough in-between them. Form the dough into a rough ball then flatten it between the two pieces of parchment by pressing down with your hand. Then roll the dough out to be ~1/4 inch thick or thick enough that the the dough won't easily tear.
Use a greased, heart shaped cookie cutter to cut cookies out. Gently lift the hearts with a spatula or your hand and place them onto the parchment-lined baking sheets evenly spaced apart. Re-roll out scraps of dough as needed and repeat this process until all of the cookie dough is used up. (Feel free to refrigerate the dough occasionally if you find it softening too much).
Bake the finished cookies for 7-12min (7-8min is usually enough for 350*F, 12min if baking at 325*F). The cookies will be soft when they first come out and should only have browned slightly around the edges and on the bottoms. Let them cool mostly on their trays, then transfer to a wire rack to speed up the cooling process. They will continue to firm up as they cool. Once the cookies have fully cooled, you can frost them!
For the frosting, simply mix the first 3 frosting ingredients in a small bowl until thick (it should be thick enough to pipe so make sure not to add too much water) then add the red or pink gel food colouring as well.
Place the frosting in a small ziplock bag and cut off a very small corner (or put it in a piping bag with a fine tip) and pipe heart outlines just slightly inside the border of the cookies. You can fill them in or just pipe the outside of the hearts.
Let the frosting harden on the cookies before serving. Enjoy your Keto Valentine's Heart Sugar Cookies!