Grease a 9-inch (22cm) square pan with about 2 tablespoons (20g) of butter. Place it in the refrigerator.
In a nonstick pan, combine the evaporated milk, water, sugar and butter. Mix well for about 5 minutes.
Place the pan on medium heat and continue stirring for about 20 minutes, until the mixture begins to thicken and the color turns light brown. The mixture should not stick to the pan. Stir very regularly.
When the mixture begins to bubble and gets a little thicker, add the vanilla essence and cardamom and mix well. Continue stirring for 5 minutes.
Add the cashews and continue stirring for another 10 minutes.
Transfer the mixture to the buttered mold.
Spread the mixture evenly over the entire surface of the mold and, while the mixture is still hot, pre-cut equal squares.