Prep the Pan: Line an 8x8-inch baking pan with parchment paper, leaving an overhang for easy removal.
Melt the Chocolate Base: In a medium saucepan over low heat, combine the chopped chocolate bars and sweetened condensed milk. Stir constantly until fully melted and smooth.
Add Flavorings: Remove from heat. Stir in vanilla extract, cinnamon, and sea salt.
Layer in Caramel: Pour half the chocolate fudge mixture into the prepared pan and spread evenly. Drop spoonful's of caramel sauce over the top, then gently swirl it into the chocolate with a knife or toothpick.
Top and Set: Add the remaining fudge mixture over the top and smooth it out. Swirl in more caramel if desired.
Chill: Refrigerate for at least 2 hours or until firm.
Cut & Serve: Lift out the fudge using the parchment paper, cut into squares.