01 - Preheat oven to 350°F. Line a 9x9 inch baking pan with parchment paper, leaving overhang for easy removal.
02 - Mix graham cracker crumbs, melted butter, sugar, and salt until combined. Press firmly into pan bottom. Bake for 10 minutes. Cool slightly.
03 - Beat cream cheese until smooth. Add sour cream and sugar, mix until creamy. Beat in eggs one at a time, then add vanilla and flour. Mix until just combined.
04 - Pour filling over crust and smooth top. Bake 35-40 minutes until center is set but slightly jiggly. Cool completely on wire rack, then refrigerate at least 2 hours.
05 - Heat sugar and water in saucepan over medium heat, swirling until mixture turns deep amber. Remove from heat, whisk in butter. Slowly add heavy cream, whisking until smooth. Add salt if using.
06 - Cool caramel slightly, pour over chilled cheesecake. Spread evenly and refrigerate for another hour.
07 - Lift bars from pan using parchment overhang. Cut into 16 squares and serve.