Preheat your oven to 350°F (175°C). Line your baking pan with parchment paper and set aside. In a large mixing bowl, whisk together the melted butter and sugar until smooth and glossy.
Add the eggs one at a time, whisking well after each to incorporate fully. Mix in the vanilla extract until combined and fragrant.
Sift in the cocoa powder, flour, and salt directly into the wet mixture. Gently fold everything together with a spatula until the batter is smooth, thick, and shiny.
Pour the batter into the prepared pan, spreading it evenly with the spatula. Bake in the oven for about 20-25 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.
Remove the brownies from the oven and let them cool completely on a wire rack. This helps them firm up for easy decorating.
In a small bowl, sift the powdered sugar and gradually stir in milk and lemon juice until you get a smooth, thick icing that flows easily from a spoon.
Transfer the icing into a piping bag or a plastic sandwich bag with the tip snipped off. Pipe small, ghostly shapes onto the cooled brownies, forming floating ‘specters’ with irregular, wispy edges.
Optionally, use a toothpick or small spatula to adjust the ‘specter’ shapes for a more haunting or whimsical look. Let the icing set for about 15 minutes before serving.
Slice the brownies with a serrated knife to get clean, ghost-like edges, then serve and enjoy their spooky, tender texture.
