Place 1 quart or 4 cups of fresh blackberries* into a bowl. Reserve a few of the blackberries for garnish if desired and set aside. In a large mixing bowl, crush the blackberries using a fork or potato masher.
Add 1/3 cup of water from the 2/3 cup + 2 Tablespoons cold water total to the crushed blackberries; press through a fine mesh strainer to remove the large seeds and cores into a medium sized saucepan.
Add 1/2 cup of the granulated sugar from the 1 cup granulated sugar and the 2 teaspoons lemon juice to the blackberry mixture. Heat on medium heat until bubbly.
Combine the remaining 1/3 cup water with the 3 Tablespoons cornstarch; whisk into the blackberry mixture and continue to stir over medium heat until mixture thick.
Remove from heat, Dissolve the gelatin with the remaining 2 Tablespoons cold water; stir into blackberry mixture. Allow the mixture to cool to room temperature.
Once blackberry mixture is room temperature, place the 1/4 cup granulated sugar with the 1 cup of the heavy whipping cream in the bowl of a stand mixer or use a large mixing bowl and electric mixer. Whip the heavy whipping cream and sugar until soft peaks form.
In a separate mixing bowl, whip the 3 oz. softened cream cheese until fluffy; fold into the sweetened whipped cream.
Spread the whipped cream and cream cheese mixture into the cooled pie shell. Gently top the cream mixture with the cooled blackberry mixture. Chill at least 2 hours to allow the blackberry mixture to set.
Whip the additional 1 cup of heavy whipping cream with 1/4 cup granulated sugar for the top of the pie. Garnish the pie with additional blackberries if desired