Soak the whole wheat berries overnight or for 8 hours in plenty of water.
Drain the water completely. Grind the soaked wheat in a wet grinder or heavy-duty mixer to make a smooth paste, adding water gradually as needed.
Filter the ground wheat paste through a fine muslin cloth or strainer 2 to 3 times to extract clean, smooth white wheat milk.
Pour the extracted milk into a wide bowl, cover and let it sit undisturbed to ferment for 10 hours.
The next day, a clear layer of water will separate on top. Without disturbing the thick sediment at the bottom, gently discard the top water layer. You will get approximately 1 1/2 cups of thick fermented wheat milk.
In a deep, heavy-bottomed kadai or pan, add the thick wheat milk, 6 cups of water and 2 cups of sugar. Stir well until the sugar dissolves completely. Check for taste and add 1/2 cup more if needed. Reserve 1/2 cup of sugar for caramalisation.
Bring the mixture to a boil over medium heat. Continue cooking for 50 minutes to 1 hour, stirring every 3 minutes to prevent the mixture from sticking or burning at the bottom. You can partially cover the pan.
In the mean time, take 1/2 cup of sugar in a pan and melt the sugar in medium heat without adding water. Melt the sugar and keep mixing till it caramalize and becomes golden brown in color. Keep the flame low to medium and make the caramel otherwise sugar will burn and spoils the taste of the sweet.
Once the mixture thickens, add the caramalized sugar and mxi well. Halwa starts leaving the sides of the pan and turns glossy, add the roasted cashews. Halwa will get the natural brown color once you add the caramalised sugar.
Start adding ghee 2 tablespoons at a time, stirring continuously. The halwa will absorb the ghee and become slightly heavy to stir; keep adding ghee in small batches and stirring.
Continue until the halwa starts releasing/oozing the ghee back out and effortlessly rotates with the ladle. Stop adding ghee and collect the excess oozed-out ghee into a separate bowl.
Turn off the flame and let the halwa rest in the pan to thicken further as it cools. Store in an airtight container once cool, or reheat in the microwave and enjoy warm! You can also reheat it in a kadai and ghee will ooze out everytime you reheat it. You can collect the ghee and serve the halwa warm. Tastes the best.
It stays good for one week when refrigerated. You can use the collected ghee to make another sweet or use in your regular cooking.