Process the strawberries, blueberries and cornstarch in a food processor until smooth. Press the puree through a fine mesh sieve into a small saucepan. Discard the seeds and pulp.

Remove from heat and stir in the vanilla.

Transfer the jam to a bowl and set aside to cool to room temperature, about 40 minutes.

Line the bottom of a 9-inch square pan with foil or parchment paper: set aside.

In a medium bowl, combine the graham crumbs and melted butter. Mix until crumbs are well coated with butter.

Press the mixture firmly into the bottom of the prepared pan. Set in the freezer while you make the filling.

In the bowl of a stand mixer fitted with the paddle attachment or with a handheld electric mixer, beat the cream cheese on medium speed until smooth and creamy, about 3 minutes.

Add the confectioners’ sugar and mix on low speed until the sugar is moistened. Then turn the speed up to medium and continue mixing until well combined, about 2 minutes.

Add the vanilla, lemon juice, and salt. Mix on medium speed until well incorporated, about 1 minute.

If using a stand mixer with paddle attachment, switch to the whisk attachment and add the cream. Beat on low speed until the cream is well mixed in. Turn the speed up to high and beat until the batter becomes thick and almost stiff, about 3-5 minutes.

Pour the filling over the prepared crust and spread evenly to the edges of the pan.

Drop spoonfuls of jam evenly over the top. Use a butter knife to swirl the jam into the filling.

Refrigerate the cheesecake for at least 8 hours.