Pulse the chocolate cookies in a food processor until they are fine. Mix the crushed cookies with melted butter until the mixture resembles wet sand.
Press the cookie mixture firmly into a 9x13 glass dish. Freeze it for 15 minutes to allow it to set.
Beat the softened cream cheese, 1/2 cup powdered sugar, and vanilla extract together until the mixture is smooth. Spread this mixture evenly over the chilled cookie crust.
Puree the strawberries with granulated sugar and cornstarch. Simmer the puree until it thickens and becomes translucent. Allow it to cool completely before spreading it over the cream cheese layer.
Puree the blueberries along with granulated sugar and cornstarch. Simmer until the mixture turns deep indigo and thick. Let it cool completely before spreading it over the strawberry layer.
Whip the heavy cream with the remaining powdered sugar until stiff peaks form. Pipe swirls of whipped cream onto the top layer of the dessert.
Garnish the dessert with red, white, and blue star sprinkles.
