Adjust the oven rack to the middle rack and preheat oven to 350°F.

Make the crust, add the gram cracker crumbs, and sugar into a medium bowl and combine and then stir in the melted butter. Mixture will be sandy. Pour into an ungreased 9-inch or 10-inch springform pan. Softly pat the crumbs down into the bottom and partly up the sides to make a compact crust. Pre-bake for 10 minutes. Remove from the oven and wrap the hot pan in piece of heavy duty foil.

Make the filling, with a stand mixer fitted with a paddle attachment, beat the cream cheese and granulated sugar together on medium-high speed until the mixture is smooth and creamy, about 2 minutes. Add the sour cream and vanilla paste then beat until fully combined. On medium speed, add the eggs one at a time, beating after each addition until just blended. Don’t overbeat the eggs, that can cause the cheesecake to sink. I like to turn off the mixer after the last egg is mixed and fold the batter together by hand to make sure there are no lumps.

Place the pan inside of a large roasting pan. Pour the cheesecake batter on top of the crust and smooth it into an even layer. Carefully pour the hot water inside of the pan up to a one-inch depth. Place in the oven.

Bake cheesecake for 55–70 minutes or until the center is almost set. If you notice the cheesecake browning too quickly on top, tent it with aluminum foil halfway through baking. When it’s finished, the center of the cheesecake will slightly wobble if you gently shake the pan. Turn the oven off and open the oven door slightly. Let the cheesecake sit in the oven in the water bath as it cools down for 1 hour. Remove from the oven and water bath, then cool cheesecake completely uncovered at room temperature before placing in the fridge to set for at least 4 hours or overnight.

For the sauce, in a medium saucepan over medium heat, add the blackberries, sugar, and lemon juice. Cook for about 5 minutes until the blackberries are masheable and softened. Remove from the heat and pour over a sieve. Discard the seeds and chunks and place the blackberry sauce into the same saucepan. Mix the corn starch and water together until smooth. Pour into the blackberry sauce and whisk until incorporated. Place over low heat and whisk constantly until the mixture starts to slightly thicken. Remove from the heat and continue to stir for a few minutes while it cools.

Pour sauce over cheesecake and enjoy!