Bring the milk to a boil in a large non-stick kadai on high heat. Add the alum and sugar, and continue to cook, stirring continuously, for about one and a half hours, or till the milk becomes grainy and begins to thicken. Add the glucose and stir well. Add the ghee and cook for a few minutes longer, stirring continuously, till the mixture begins to leave the sides of the kadai.
Sprinkle four tablespoons of water and stir. Cook, stirring continuously, till the mixture turns brown. Transfer onto a ten by eight-inch greased tray and tap the tray on the tabletop to spread it evenly. Sprinkle the nuts and leave to set for four to five hours before cutting into squares.