Preheat oven to 350F (180 C) and line the bottom of tart with parchment paper. Butter the edges of the tart pan.
Place the graham cracker's crumbs, sugar and melted butter, in medium bowl and combine. Transfer crumbs inside the tart pan and press the crumbs with a measuring cup or cake spatula. Bake the crust for 5-8 minutes. Cool and set aside.
In the bowl of a stand mixer, whisk the cream cheese for 10 minutes or until creamy and fluffy. Add sugar and beat until combined. Add eggs, one at a time, vanilla extract and flour. Beat until well combined. Pour cheesecake filling into cooled crust. Level the filling with spatula & set aside.
In a medium bowl, combine sweetened condensed milk, egg yolks and key lime juice. Whisk slowly first, then speed up the mixing & mix until smooth. Pour the key lime mixture on top of the cream cheese filling. Smooth out and level with spatula.
Bake in a preheated oven 350F (180C) for 35 minutes or until cheesecake is set and jiggles only slightly in the centre. Cool the cheesecake for 20 minutes, then chill in refrigerator for 6 hours, better overnight.
For the whipped cream dollops, combine 35% whipping cream, confectioner (icing) sugar and vanilla in the bowl of an electric mixer. Start whipping on low speed, increase the speed gradually and whip on high until stiff peaks forms. Transfer the whipped cream into a pastry bag with a round tip. Pipe little dollops of whipped cream all of over cheesecake. Garnish with fresh lime zest on top & serve!