In a large mixing bowl, whip the heavy cream, powdered sugar, and vanilla extract until soft peaks form.
In another bowl, beat the softened cream cheese until smooth.
Gradually fold the whipped cream into the cream cheese until well combined.
In a 9x13 inch baking dish, spread a thin layer of the cream mixture on the bottom.
Place a layer of graham crackers over the cream mixture, breaking them as needed to fit.
Spread half of the remaining cream mixture over the graham crackers, then add half of the mixed berries on top.
Repeat the layers with another layer of graham crackers, the remaining cream mixture, and the remaining berries.
Finish with a final layer of graham crackers on top.
Cover the dish with plastic wrap and refrigerate for at least 4 hours, or overnight for best results.
Before serving, top with the additional mixed berries. Slice and serve chilled.