Preheat your oven to 350 degrees Fahrenheit and line a baking sheet with parchment paper. Set aside.
In a large bowl, whisk together the gluten free flour, cocoa powder, baking powder and salt. Set aside.
Measure out 1 cup milk of choice. Add the one tablespoon of white vinegar into the milk and stir. Let sit for 5-10 min and then stir again. It will look chunky and that’s normal. Set aside.
In a small bowl using a spoon, mix together the cornstarch and water until thin and watery. It will be thick and tacky at first. Set aside.
In the bowl of an electric mixer using the paddle attachment or in a large bowl using a hand held mixer, beat the softened butter or vegan baking stick until soft and creamy. About 1-2 minutes.
Add the brown sugar on medium speed and beat until fluffy and combined.
Beat in the cornstarch water mixture, you may need to stir it a second time if it got tacky again. Once combined add in the milk vinegar mixture and vanilla. Scrape down the sides of the bowl as needed.
Then on slow speed, slowly add in the dry ingredients and mix until just combined. Add in the red food coloring and mix until combined and your batter turns a deep red color.
Using an ice cream scoop or cookie scoop, spoon batter onto prepared baking sheets making sure to leave 2 inches in between each cookie. Get your fingers wet and gently using your fingers, press down the batter to make a dome instead of a ball. Gluten free flour has a way of staying exactly as it is placed down, so if you leave it in a ball shape or misshapen, that’s how it will end up.
Bake for 16-17 min and let cool on the baking sheet. While they are cooling, make the filling.
For the filling: In a small saucepan set over medium heat, combine the frozen raspberries and granulated sugar. Stir constantly for about 5 minutes until the raspberries have liquified and the sugar has dissolved. Use the back of your spoon to mash the raspberries apart.
Set a strainer or a mesh colander over a bowl and strain the raspberries. You don’t want any of the seeds, you just want the liquid. You should have about 1 tablespoon of liquid.
With the paddle attachment of an electric mixer, or using a large bowl and a hand mixer, beat the softened vegan baking stick until creamy. Add the confectioners’ sugar, water, strained raspberry liquid (1 tablespoon) and vanilla. Beat till smooth and combined. If the raspberry liquid solidified a bit, that’s ok. Just use a spatula to scrape it into your mixing bowl.
NOTE: To make the filling with dairy, use softened butter instead of the vegan baking stick. Enjoy!