• Preheat the oven to 350°F.
• Cut parchment paper for the bottom of your two 9-inch cake pans and spray with gluten-free cooking spray. (I like coconut oil cooking spray.)
• Add the white vinegar (or lemon juice) to the milk to make the homemade buttermilk.
• In a medium-sized bowl, add the gluten-free flour with xanthan gum, salt, baking soda, gluten-free baking powder, cocoa powder, and cinnamon. Stir to combine the ingredients.
• In a large bowl, cream the softened butter and granulated sugar with a mixer until fluffy.
• Add the eggs and pure vanilla extract to the butter mixture and mix until fully combined.
• Add the gluten-free flour mixture to the butter mixture and mix until fully combined. Scrape down the sides if needed.
• Add the homemade buttermilk to the cake batter and mix until fully combined.
• Add the boiling water to the batter and mix until fully combined.
• Pour half of the batter into the first 9-inch cake pan and then pour the rest of the batter into the second 9-inch cake pan.
• Bake on the middle rack for 30-35 minutes. Please watch your cakes because all ovens are different. Check the center of the cake by inserting a toothpick to make sure it is done. You will also see the sides of the cake pulling away from the side of the pan.
• Allow the cakes to cool for 15 minutes. Remove them from the cake pans and allow to fully cool on a baking rack.
• Wrap the cakes in plastic wrap or foil and then place in a freezer bag. Freeze the cakes overnight or for a minimum of 6 hours.

Ice Cream Layer

• Take the gluten-free ice cream out of the freezer and allow it to soften for 5 minutes.
• Line a 9-inch cake pan with aluminum foil or plastic wrap. I like using foil because it does not lift up when you add gluten-free ice cream to the pan.
• Empty the entire container of softened, gluten-free ice cream into the cake pan and smooth it out with a spatula.
• Cover the smoothed top with foil or plastic wrap and freeze the ice cream overnight or for a minimum of 6 hours.

How To Assemble The Ice Cream Cake

• Crush the gluten-free cookies either in a food processor or place them in a plastic storage bag and crush them with a rolling pin.
• Make the whipped cream frosting.
• Place the first cake layer on top of the cake platter.
• Add a thin layer of whipped cream to the top of your cake layer and sprinkle with some of the crushed gluten-free cookies. 
• Remove the frozen ice cream layer from the foil and place it on top of the first cake layer. 
• Sprinkle the top of the ice cream layer with some crushed gluten-free cookies.
• Place the second cake layer on top of the ice cream layer. 
• Cover the whole cake with the whipped cream frosting. If using the dairy-free Cocowhip, it will be softer than the stabilized whipped cream. When using the dairy-free Cocowhip, I just frosted the top of the cake.
• Using a star tip (Wilton 1M tip), add some dollops of whipped cream on top of the cake. Finish decorating with additional whole gluten-free cookies and remaining crushed gluten-free cookies.
• Serve immediately or place the cake back into the freezer until ready to serve.
• Just before serving, take the cake out of the freezer and move it to the refrigerator for 30 minutes or let sit at room temperature for 15 minutes for easy slicing.
• Store leftovers in a freezer-safe container and place the cake back in the freezer. 

Whipped Cream Frosting

• Place your mixing bowl in the refrigerator or freezer for a few minutes to chill.
• In the cold mixing bowl, whip the heavy whipping cream on medium speed for 15-30 seconds or until it's foamy.
• Add the pure vanilla extract, powdered sugar, and cornstarch and continue mixing at medium speed until stiff peaks form and it becomes firm.
• Refrigerate until ready to frost the cake.