1. Line an 8-inch square pan with parchment paper, leaving overhang on the sides for easy lifting.

2. In a small bowl, stir together the brown sugar, cinnamon, melted butter, and graham cracker crumbs until combined. Set aside.

3. In a saucepan over low heat, melt 3 cups white chocolate chips, sweetened condensed milk, 4 tablespoons butter, and salt, stirring constantly until smooth.

4. Remove the pan from the heat and stir in 1 teaspoon vanilla extract.

5. Pour half of the fudge mixture into the prepared pan and spread it evenly.

6. Spoon the cinnamon mixture over the fudge in small dollops.

7. Top with the remaining fudge mixture and gently spread to cover.

8. Use a knife or skewer to lightly swirl the layers together without overmixing.

9. In a microwave-safe bowl, melt 1 cup white chocolate chips with the heavy cream in short bursts, stirring until smooth.

10. Stir the softened cream cheese and 1/2 teaspoon vanilla extract into the topping until creamy.

11. Drizzle the topping over the fudge in lines to mimic cinnamon roll icing.

12. Refrigerate for at least 3 hours, or until fully set.

13. Lift the fudge from the pan, slice into squares, and dust lightly with cinnamon if desired.