Add the ghee and semolina to iron kadhai (or cast iron pan). Mix well for 2 minutes so that you see all the semolina is covered in ghee. Place the kadhai on a low medium stove and begin roasting the semolina. You will have to keep an eye and keep stirring frequently for it can burn easily.
While the semolina is roasting, add the sugar and water to a small sauce pan or pot and set on the other stove on medium heat. In about 5-8 minutes, the sugar will dissolve in water. Switch off the stove, dont cook the syrup. We dont want any string consistency or anything. Keep the syrup near and warm.
Coming back to semoilina, keep on roasting it while stirring it making sure to scrape it from the bottom of the kadhai, it burns that way easily. Roast the semolina for good 10- 15 minutes(see notes) till you see that the ghee has begun to seperate and the semolina granules are dark brown in color. There should be no black specks of semolina- that means the semolina has burnt, a conistent medium heat and contuinal stirring ensures that wont happen.
Reduce the stove to low, and slowly add the warm sugar syrup from one side of the kadhai to the semolima while stirring it at the same time with the other hand, this makes sure that no lumps are formed. There will be spluttering so watch out.
As soon as the syrup is added, you will see a puddle followed by big bubbles in a minute on the surface of the halwa, your will notice that the semolina granules begin to swelled up. it will be runny, let the halwa cook on low heat. Add the raisins, almomds and black cardamom powder now.
Keep stirring everything gently and continue to cook the halwa for 3-4 minutes on low heat. Add 1-2 tbsp of ghee (if you wish)and mix well. The halwa will be glistening and of thick smoothie like pourable consistency by the end of 5-6 minutes. Dont let all the liquid absorb. Switch off the stove. Mix in the rose water. The halwa will thicken as it sits.
Serve warm garnished with nuts. Enjoy!