Set the oven to 350 degrees and line a quarter sheet pan with parchment paper.
In a large glass bowl, combine the chocolate and butter and microwave in 30-second increments or until melted. Stir to combine. Add the sugar, salt, and vanilla and stir again. Add the eggs and stir until thoroughly incorporated. Lastly, add the flour and gently fold to combine.
Pour into the lined sheet pan and smooth into an even layer.
In another bowl, combine the cream cheese, powdered sugar, egg, and flour and whisk together until smooth.
Drop spoonfuls of the cream cheese mixture over the brownie batter. Repeat with the marmalade. Use a wooden skewer or the tip of a sharp knife and swirl together the cream cheese, marmalade, and batter.
Place the sheet pan in the middle of the oven and bake until the mixture is set and the top of the brownies begins to crinkle, about 20 minutes. Cool completely before slicing and serving.