Preheat your oven to 350°F (175°C).
In a microwave-safe bowl, combine the coarsely chopped unsweetened chocolate and cubed unsalted butter. Microwave in 30-second intervals, stirring in between, until melted and smooth.
Let the mixture cool for a few minutes, then stir in the sugar. Add the eggs one at a time, mixing well after each addition. Add the vanilla extract and salt, stirring until combined.
Gently fold in the all-purpose flour with a spatula until just combined.
Fold in the cut-up Fun Size Twix bars into the brownie batter.
Pour the brownie batter into the prepared baking pan and bake for 25-30 minutes, or until a toothpick comes out with a few moist crumbs.
While the brownies are baking, prepare the caramel topping by combining the caramel candies and heavy cream in a small saucepan over low heat. Stir until smooth.
Once the brownies are out of the oven, cool for 10 minutes, then drizzle the caramel mixture over the top.
Let the brownies cool completely in the pan before cutting into squares.