Preheat oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan.

In a large bowl, whisk together the gluten-free flour, cocoa powder, baking soda, and salt.

In a separate bowl, combine the sugar, oil, vanilla extract, buttermilk, and egg. Beat well.

Gradually add the wet ingredients to the dry ingredients, mixing until just combined. Do not overmix.

Pour the batter into the prepared pan and bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.

Let the cake cool completely in the pan before frosting.

In a large bowl, beat the softened cream cheese until smooth.

Gradually add the powdered sugar, beating until smooth and creamy.

Stir in the vanilla extract.

Using a round cookie cutter (about 3 inches in diameter), cut out circles from the cooled cake.

Spread a generous amount of filling on the flat side of half of the cake circles. Top with the remaining cake circles to create a sandwich.

Place the sandwiches in the freezer for about 30 minutes to firm up.

In a microwave-safe bowl, melt the chocolate chips and shortening together in 30-second intervals, stirring in between, until smooth.

Dip each frozen cake sandwich into the melted chocolate, coating completely. Place on a parchment-lined baking sheet to set.

Refrigerate for at least 15 minutes to allow the chocolate to set completely.