• In the bowl of a stand mixer (or a large bowl and a hand mixer), combine the ground flaxseeds and water and let it sit for 15 minutes, or until thickened.
• Preheat the oven to 350 degrees fahrenheit (177 degrees celsius). Line 3 baking sheets with parchment paper. In a medium-sized bowl, whisk the GF flour, cocoa powder, baking soda, baking powder, and salt together. Pour the sugar and brown sugar into the thickened flax/water mixture and beat on high (using the paddle attachment) until combined. Add the soft butter and beat on high until there are no large chunks. Add 1/3 of the mixed dry ingredients. Mix on low and gradually move to high speed until well combined and there are no more butter lumps. Add the vanilla, apple cider vinegar, and half of the almond milk and mix well. Pour in half of the remaining dry ingredients and mix on low until just combined. Add the rest of the dry ingredients and mix on low, gradually working your way up to high speed. Scrape the sides of the bowl with a spatula. Mix on medium-speed. While the mixer is running, drizzle in the rest of the almond milk then crank up the speed to high and beat until smooth and slightly fluffy.
• Using a cookie scoop, scoop "pies" onto each baking tray with space in between each one so they don't bake into each other (maximum of 12 per tray). Bake for 9-11 minutes or until you can gently nudge one and it springs back (sort of a cake-like texture). Remove the trays from the oven, and let them cool (on the pans) completely.

For the Filling:

• In the bowl of a stand mixer (or a large bowl and a hand mixer), beat the butter, salt, and vanilla (using the whisk attachment) until smooth. Add half of the powdered sugar and beat until combined. Add the rest of the powdered sugar and beat until pale and fluffy. Pour in the marshmallow creme and mix until well combined. Trandfer the filling to a piping bag fitted with a large round tip.

To Assemble

• Flip half of the "pies" upside down. Pipe a blob of filling on top of each and place in the fridge for at least 20 minutes to prevent the filling from oozing all over the place and making a mess. After 20 minutes, place an unfrosted "pie" on top, sandwiching two together. Repeat with the remaining "pies" and filling. Serve immediately or store in the fridge until you're ready to eat. Enjoy!