1. Make the demerara syrup: In a large pot set over high heat, combine the demerara sugar and water and heat, stirring occasionally until dissolved. Set aside to cool and store in the refrigerator.
2. Make the cocktail: In a mixing glass, combine the bitters, 1 teaspoon of the reserved demerara syrup, Scotch, bourbon and apple brandy. Stir the ingredients. Pour into a rocks glass filled with ice. Serve.