Preheat oven to 350 degrees F. Coat a 13x9x2-inch baking pan with nonstick vegetable oil spray. In a large bowl, combine the graham cracker crumbs, shortbread cookie crumbs and cinnamon. Add the melted butter and stir until the mixture is coated. Using your fingers, press the mixture evenly onto the bottom of the baking pan. Bake for about 10 minutes or until the crust is golden. Transfer the pan to a rack and allow to cool completely.

In a stand mixer or food processor blend the cream cheese and sugar until smooth and creamy, stopping periodically to scrape down the sides of the bowl (about 2 minutes). Add the eggs one at a time and process in between each addition for about 5 seconds to blend. Add the dulce de leche and vanilla extract and process until blended (about 20 seconds). Spread the batter evenly over the cooled crust and bake for about 30 minutes or until just set in the center and the edges are puffed and slightly cracked. Transfer the pan to a rack and allow to cool completely.

In a small saucepan over medium-low heat, warm 4 tablespoons of heavy whipping cream (about 1 minute) and whisk in the dulce de leche until smooth and creamy. If the dulce de leche mixture is too thick to be poured, add additional cream, 1 teaspoon at a time, until a pourable consistency is reached. Pour the glaze over the cooled cheesecake and slightly tilt the pan from side to side and front to back until the glaze is spread evenly. Refrigerate to chill for at least 1 hour. To serve, cut the cheesecake lengthwise, wiping the knife in between, in 4 strips and then crosswise into 6 strips. Sprinkle each bar with fleur de sel to taste.

Make Ahead:

This recipe can be made 1 day ahead and stored in the refrigerator until serving.