Add the blackberries to a skillet set over medium heat. Allow them to cook, stirring occasionally, until the blackberries start to break down- about 5 minutes.
Add the cream cheese and vanilla extract to the pan, and stir until smooth and evenly incorporated.
Remove the skillet from the heat and set aside, allowing the mixture to completely cool.
Chill a large metal mixing bowl in the fridge for 30 minutes, then add the cream to the chilled bowl. Using a hand mixer, whip the cream until fluffy and stiff peaks have formed- DO NOT over mix.
Add the heavy cream to the mixing bowl, and stir until evenly incorporated.
Add the berry mixture to the bowl, and stir again until evenly incorporated.
Break up the graham cracker crust into small pieces, reserve a tablespoon or two. Stir the rest of the crust pieces into the ice cream mixture, leaving chunks behind is ok.
Transfer the ice cream mixture to a 9x5" metal loaf pan. Spread it out into an even layer with a spatula.
Freeze the ice cream for at least 6 hours, but up to overnight.