Add the blueberries, sugar, lemon juice, vanilla and cornstarch to a medium pot. Cook over medium heat for 20-23 minutes until thick. Half way through, smush some of the blueberries with the back of a wooden spoon. Remove from the heat and allow to completely cool.

Add the sugar and lemon zest to a medium bowl. Rub the lemon zest and sugar together with your fingertips to extract the most lemon flavor from the zest.

Add in the butter and vanilla. Cream together with an electric mixer on high speed for 1 minute until light and fluffy.

Add in the flour and salt. Mix together on medium speed until coarse crumbs form. Pop the crumble in the fridge while working on the rest of the cheesecake.

Preheat the oven to 350° F (175° C). Prepare your 9-inch springform pan for its later water bath by wrapping the bottom and sides with tinfoil.

Pulse the Nilla Wafers together in a food processor until they are finely ground. Then add in the melted butter and sugar and pulse until combined.

Press the cookie crumbs into the bottom and up the sides of the pan, about 1 inch. Bake the crust for 10 minutes and then let it cool completely.

In the bowl of a stand mixer, mix the cream cheese, sugar and cornstarch together with a paddle attachment for two minutes on medium speed until everything is smooth and there are no lumps.

Add in the sour cream, lemon zest and vanilla. Mix for 1 minute on medium speed.

Next add in the eggs and egg yolks one at a time to the cheesecake batter. Mix on low speed, ensuring that each is fully mixed in before adding the next.

Pour half the batter into the prepared pan with the crust, then use an offset spatula to smooth it out into an even layer. Spoon half of the blueberry jam over the batter. Gently swirl the jam and cheesecake batter together with a butter knife.

Pour the rest of the batter in the pan and smooth it out with an offset spatula. Spoon the rest of the jam on top. Gently swirl the jam with a butter knife.

Sprinkle the chilled streusel over the top. Place the cheesecake in a large roasting pan in the oven. Slowly pour the boiling water into the pan around the cheesecake being careful not to splash the cheesecake.

Bake at 350° F (175° C) for 1 hour and 15 minutes. When 1 hour 15 mins are up, turn the oven off and crack the oven door open using a wooden utensil. Let the cheesecake stay in the oven for 1 more hour.

Once the 2 hours and 15 minutes are up, remove the cheesecake from the oven and carefully go around the edges of the pan with a butter knife to loosen the crust from the sides of the pan. Let the cheesecake cool completely on the counter, and then refrigerate until completely cold, 8 hours or overnight.

Add the heavy cream and powdered sugar to a bowl. Mix on high speed with an electric mixer until stiff peaks form, about 1-2 minutes.

Remove the cheesecake from the springform pan and transfer it to a serving plate. Pipe whipped cream around the edges of the cheesecake. Decorate with blueberries and lemon slices if you wish. Then, serve!