Bake the cookies following Smitten Kitchen's recipe or buy them. If you choose to bake them, make sure you roll out the dough as thin and evenly as possible before baking. The cookies can be baked the day before. Break them into pieces and store covered.

Put the cookies or cookie pieces into a food processor and pulse until they are fine crumbs. Remove the crumbs from the bowl, measure out 4 cups of crumbs, and put them back into the food processor. Add the flour and pulse to combine. Add the melted butter and pulse until the cookie crumbs have the consistency of wet sand.

Press about 2 cups the crust into the bottom of the 9' springform pan and then the rest up the sides of the pan to the top edge. You should use all of the crust mix.

Preheat oven to 325 degrees.

Put the milk in a small pot. Split open the vanilla bean and scrape out the seeds inside. Put both into the pot with the milk. Heat the milk until it's hot, but not boiling. Turn off the heat and let the vanilla and milk steep for 15 minutes. Remove the vanilla pod and whisk the seeds into the milk.

For the filling, put the cream cheese into a mixing bowl. Add in the sugar and beat until combined with the cream cheese and very smooth. Crack the eggs into a separate bowl, and with the mixer on, slowly beat in the eggs one at a time. Stop the mixer and scrape down the sides with a spatula. Turn it on again and add in the milk with the vanilla beans, beat until it's all combined and there are no lumps.

Pour the filling into the pan with the crust. Place the pan on a cookie sheet lined with foil. Bake for 55 min-1 hour at 325 degrees until set but still soft and jiggly in the center.

While the cheesecake is cooking, mix together the sour cream, sugar and vanilla. When the cheesecake is done, remove from the oven for 10 minutes, but leave the oven on. After 10 minutes, spread the sour cream topping on the cheesecake and return to the oven for 10 more minutes. Remove, place on a cooling rack and allow to cool for 1 hour. Refrigerate before adding the caramel topping for at least 4 hours.

In a small, heavy bottomed pot, melt the sugar with water. Cook over high heat until deep amber in color. Remove from heat, and carefully whisk in the cream. Whisk in the butter, and if the caramel has cooled too much to melt the butter, return to a low heat and whisk until it is all incorporated. Whisk in the 1 tsp fleur de sel.

Allow the caramel to cool and pour over the top of the baked and cooled cheesecake. Once the caramel is set, garnish the top with flakes of fleur de sel.