Start by making the caramel filling so it can thicken. In a heavy saucepan over medium heat, combine the sweetened condensed milk, 1/2 cup butter, brown sugar, corn syrup, and salt. Stir frequently until the mixture begins to bubble. Lower the heat and let it simmer, stirring frequently, until it thickens and turns a medium caramel color, about 10 minutes. Remove from heat, stir in the vanilla extract, pour into a container, and set aside to cool.

Preheat the oven to 350°F. Grease an 8-inch springform pan with non-stick spray and place a parchment round on the bottom. For the crust, combine 1/2 cup butter, flour, powdered sugar, and 1/4 tsp salt using a fork or pastry cutter until it forms a soft dough. Press the dough into the pan to create an even layer. Prick the crust with a fork and bake for 22-25 minutes until the edges start to brown. Cool on a wire rack.

Lower the oven to 300°F and place a baking tray with about an inch of water on the bottom rack. For the cheesecake filling, whisk together sugar and cornstarch in a small bowl. Beat the cream cheese and sugar mixture on low speed until smooth. Gradually add the whisked eggs, mixing on low speed. Mix in the sour cream, caramel, and vanilla extract until just combined. Pour the batter into the prepared pan. Bake at 300°F for 20 minutes, then reduce the temperature to 225°F and bake for another 2 hours. Let the cheesecake sit in the oven for 1 hour with the door closed, then cool at room temperature. Refrigerate for 3-4 hours or overnight.

To make the ganache, heat the heavy cream in the microwave for 45 seconds. Pour over the chocolate chips and let sit for 1 minute. Stir until smooth, then mix in the butter, corn syrup, and salt. Cover and set aside to cool to room temperature.

Once the cheesecake is cooled, spread the room-temperature caramel on top and chill for 10 minutes. Spread the chocolate ganache over the caramel. Sprinkle with flaky sea salt. Cut with a warm, sharp knife, cleaning after each cut. Store leftovers in an airtight container in the fridge for up to a week.