Crust
14 tablespoons unsalted butter, melted and still warm
1/2 cup (3.5 oz) sugar
2 teaspoons vanilla extract
3/8 teaspoon salt
2 cups (9 oz) all-purpose flour
Filling
3/4 cup caramel sauce (recipe below)
1 1/2 lbs cream cheese, at room temperature
1/4 cup (1.75 oz) sugar
1 1/2 teaspoons vanilla extract
2 large eggs, at room temperature
To make the crust: Preheat oven to 350 F with a rack in the lower third of the oven. Line a 13x9 baking pan with parchment paper, leaving an overhang so you can lift the bars out after they've baked.
Combine the melted butter, sugar, vanilla and salt in a medium bowl. Stir in the flour until just incorporated - the mixture will be soft, that's fine. Transfer the mixture to the prepared baking pan and press into an even layer on the bottom of the pan. Bake for 20-25 minutes, or until the crust is golden brown. Let cool completely. Turn the oven down to 325 F.
To make the filling: In the bowl of a stand mixer fitted with the paddle attachment, beat the cream cheese on medium speed until smooth, about 30 seconds. Scrape down the sides of the bowl then add the sugar and vanilla, beating until smooth and creamy, about 1-2 minutes. Add the eggs, one at a time, beating just until incorporated and scraping down the sides of the bowl in between. Transfer 2 tablespoons of this batter to the 3/4 cup of caramel sauce and stir to incorporate. Pour the remaining cheesecake batter over the cooled crust and spread evenly.
Dollop the caramel sauce mixture over the filling. Use a toothpick to gently marble the caramel, being careful not to scrape the crust while you are doing it. Bake for 20-25 minutes, or until the edges are puffed and the center is just barely set.
Transfer the pan to a cooling rack and let come to room temperature. Cover and refrigerate for at least 4 hours, but preferably 24. Use the parchment sling to lift the bars out of the pan and transfer to a cutting board. Cut into squares with a long sharp knife. The bars can be refrigerated in an airtight container for up to 4 days.
Salted Caramel Sauce - adapted from Cook's Illustrated
2 cups sugar
1 cup heavy cream
2 tablespoons cold unsalted butter
1 teaspoon flour de del or grey sea salt
Add 1 cup of water to a 2-qt saucepan. Gently add the sugar to the center of the pot - it will mound, that's fine. Cover the pot and bring to a boil over high heat. Once boiling, uncover the pot and insert a candy thermometer. Continue cooking until the mixture registers 300 F and is just starting to develop some color, about 15 minutes. Reduce heat under the pot to medium and cook until the syrup is amber and registers 350 F on the thermometer, about another 5 minutes. Meanwhile, pour the cream into a small saucepan and bring to a simmer. If it simmers before the syrup is ready, just take it off the heat and set aside.
Remove the caramel from the heat and add about 1/4 of the warm cream to the pot. It will bubble furiously so be careful. Once the bubbling subsides, add the remaining cream. When it stops bubbling, whisk gently to incorporate fully. Add the butter and the salt and whisk to combine.
Set aside 3/4 cup of the salted caramel sauce for the cheesecake bars. The remainder can be refrigerated for up to 1 month.
Makes about 2 cups