Prep the Blueberry Swirl: In a small saucepan, combine 1 cup fresh blueberries, 1/4 cup granulated sugar, 1 tbsp lemon juice, and 1 tsp cornstarch. Add 1/4 cup water and stir to combine. Cook over medium heat, stirring frequently, until the mixture thickens and becomes syrupy, about 8-10 minutes. Remove from heat and let it cool completely. Once cooled, blend until smooth and strain to remove any skins. Set aside.

Make the Red Velvet Cake: Preheat your oven to 350°F (175°C). Grease and line two 9-inch round cake pans with parchment paper. In a medium bowl, whisk together 2 cups flour, 1 cup sugar, 1 tsp baking soda, and 1 tsp salt. In another bowl, combine 1 cup buttermilk, 1/2 cup vegetable oil, 2 eggs, 2 tbsp red food coloring, 1 tsp vanilla extract, and 1 tsp white vinegar. Mix well. Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Divide the batter evenly between the prepared pans.

Bake the Cakes: Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean. Allow the cakes to cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.

Assemble the Ice Cream Cake Base: Line a 9-inch springform pan with plastic wrap, leaving an overhang for easy removal. Place one layer of the red velvet cake at the bottom of the pan. Spread a thin layer of the blueberry swirl over the cake. Arrange 6 vanilla ice cream sandwiches in a single layer on top of the blueberry swirl, breaking them if necessary to fit. Spread half of the slightly softened vanilla ice cream evenly over the ice cream sandwiches. Drizzle a few tablespoons of the blueberry swirl over the ice cream. Freeze for 30 minutes.

Add the Second Cake Layer: Place the second red velvet cake layer on top of the ice cream. Spread the remaining vanilla ice cream evenly over the cake layer. Drizzle the remaining blueberry swirl on top. Arrange the remaining 6 ice cream sandwiches on top, pressing gently to adhere. Freeze for at least 2 hours or until firm.

Whip the Cream: In a chilled bowl, whip 1 cup heavy whipping cream, 2 tbsp powdered sugar, and 1/2 tsp vanilla extract until stiff peaks form. Spread or pipe the whipped cream over the top of the frozen cake. Garnish with fresh blueberries, raspberries, and mint leaves.

Freeze and Serve: Freeze the cake for at least 1 hour before serving to set the whipped cream. To serve, remove the cake from the springform pan using the plastic wrap overhang. Slice and enjoy!