For the crust:

1. Line an 8 inch square baking dish with parchment paper, leaving about a 2-inch overhang on all sides so you can easily remove the bars. 
2. In a medium bowl whisk together the graham cracker crumbs, sugar and melted butter until combined. Press the mixture into the bottom of the prepared pan and refrigerate until firm, about 45 minutes. Meanwhile, make the filling. 

For the cheesecake:

1. Add the cream cheese, sugar, vanilla, lemon zest and lemon juice to the bowl of a food processor or a blender. Blend until smooth, scraping down the sides as necessary. Pour the mixture into a medium bowl and fold in ½ cup of the whipped cream (see instructions below). Fold in another ½ cup of whipped cream until the mixture is smooth. Save some whipped cream to serve with. 
2. Pour the cheesecake filling over the chilled crust and smooth with a spatula. Cover and freeze cheesecake for at least 4 hours. 
3. When ready to serve, use the parchment paper to remove from the pan. Use a warm knife to cut into 9 bars (or cut smaller for more bars). Place in the refrigerator 30 minutes prior to serving. Serve with a dollop of whipped cream and some berries if desired. 

For the whipped cream:

1. Using a hand mixer or a stand mixer fitted with a whisk attachment, whip the heavy cream, sugar, and vanilla extract on medium/high speed until medium peaks form, about 3-4 minutes.