Special equipment: 1 ghost-shaped cookie cutter, no more than 5 inches long
For the salted caramel: Add 2 tablespoons water, the sugar and salt to a heavy-bottomed saucepan over medium heat. Stir to combine with a heat-proof spatula until the sugar dissolves. Bring the mixture to a boil and cook until the mixture begins to turn an amber brown color, 8 to 10 minutes. Whisk in the cream, remove the saucepan from the heat and stir in the butter, being careful because it will foam up. Adding butter at the end will stop the cooking and keep your caramel soft. Cool.
For the sandwich build: Preheat a grill pan over medium-high heat. Spread some salted caramel on one side of 4 pieces of bread. Top with the bacon and apples. Top with the remaining bread and butter both sides of the sandwiches. Place the sandwiches on the grill and cook until nice and toasted, 3 to 4 minutes, flipping halfway through. Add more butter to the pan if needed.
Once all sandwiches have been grilled, take a ghost-shaped cookie cutter and punch out ghost shapes from each. Put on a tray and watch masked children devour.