Preheat your oven to 350°F (175°C) and line a 9x9 inch baking pan with parchment paper. Bake the brownies according to your recipe or package instructions, then let them cool completely in the pan to prevent cracking.
While the brownies are cooling, prepare the sugar shell by combining the chilled sugar, water, corn syrup, vanilla, and salt in a heavy saucepan. Attach a candy thermometer and heat the mixture over medium heat without stirring, watching for it to reach 300°F (hard crack stage).
Once the sugar syrup reaches 300°F, remove the saucepan from heat and carefully pour the hot syrup into a heatproof container. Allow it to cool just enough to handle but remain pourable and glossy.
Using a spoon or a piping bag, gently spread or drizzle the warm sugar shell over the cooled brownies, creating uneven cracks and a ghostly, flaky shell. Let the coating set and harden at room temperature, which may take about 15 to 20 minutes.
Once the shells are crisp and cool, gently break or crack them slightly if needed to enhance the spooky, ghost-like appearance. This contrast between the crunchy shell and fudgy interior adds texture and visual interest.
Slice the brownies into squares or ghost-shaped pieces. Serve immediately to enjoy the satisfying crunch followed by the soft, chocolatey interior.
