Preheat oven to 350 degrees (F). Line a 9x13-inch baking pan with heavy-duty aluminum foil, allowing two of the sides to overlap (you want an overhang of at least 2-inches on two sides) and spray lightly with nonstick baking spray. Set aside.

In a large bowl combine the graham cracker crumbs, sugar, and butter and, using a rubber spatula, mix well to combine. Press the mixture into the bottom - and slightly up the sides - of the prepared pan.

Bake the crust in preheated oven for 10 minutes. Remove the crust from the oven and set aside on a cooling rack until needed.

Reduce the oven temperature to 325 degrees (F).

In the body of a high power blender, food processor, stand mixer fitted with the whisk attachment, or in a large bowl using a hand held electric mixer, beat the cream cheese and sour cream until completely smooth. 

Add sugar and vanilla and beat until smooth, scraping down the sides and bottom of bowl as needed. Add in the eggs and yolks and beat until combined.

Add in the lemon juice and lemon zest and beat until combined. Stir in the flour, mixing just until combined.

Using a rubber spatula, fold in the cream, mixing just until it's incorporated in the batter.

Pour filling on top of prepared crust, and spread evenly.

Check to ensure your oven has cooled to 325°F, then place the pan in the oven and bake for 38 to 40 minutes, or until the edges have set and the middle is still a little jiggly. The cheesecake will firm up a lot as they cool.

Remove the bars from the oven, and cool at room temperature for one hour. Then refrigerate for at least 6 hours, or overnight.

When you're ready to serve: use the foil overhang to lift the cheesecake bars from the pan and transfer them to a cutting board. Using a large, sharp knife, slice the slab into squares, wiping the knife clean with a damp cloth between slices. Serve at once.