Preheat oven to 325°F and line a 9x13 pan with parchment paper.
Combine graham cracker crumbs, sugar, and melted butter; press into pan and bake for 10 minutes.
Beat cream cheese until smooth, then add sugar, eggs, vanilla, and sour cream.
Pour batter over cooled crust and smooth top.
Mix dulce de leche with cream; drop spoonfuls and swirl gently with a knife.
Bake 40–45 minutes until edges set and center slightly jiggles.
Cool in oven 30 minutes, then chill at least 4 hours before slicing.