Mix ½ cup of corn starch and 1 cup of water without any lumps and set aside. Grease a plate generously with ghee and set it aside.
Meanwhile, mix the remaining one cup of water and sugar in a heavy bottom pan.
Bring it to a nice boil and add the lemon juice. We don't need to check for any consistency here.
Reduce the heat to medium-low and add the corn starch slurry. Make sure to mix the slurry before adding it to the sugar syrup.
Add the rose syrup as well and mix.
As the mixture slowly starts to thicken and bubble up, start adding the ghee. Add a little over 1 tbsp of ghee every three minutes. Keep stirring, and do not leave it unattended.
The halwa will become glossy and transparent slowly. Add the nuts after about 5 minutes and mix.
When we have used up all the ghee, the halwa will be shiny, and you will see ghee slowly oozing on the sides. When you drop a blob of this halwa from the spatula, it should fall without sticking in the spatula, and that's the right stage. It took approx 12~13 minutes for me to reach this consistency.
Now transfer the halwa to the greased plate and spread it evenly. Let it cool for one hour atleast before slicing.
Notes
The above measure works perfectly for me, and we love the texture of the halwa this way.
For a sweeter version of halwa, increase the sugar to 1.5 cups.
You can use the preferred flavoring of your choices, like ground cardamom or fruit essence. You can also use the food color of your choice. Traditionally orange food color is used.
Before adding the corn starch slurry to the sugar mix, mix well again as the corn starch gets deposited in the bottom. You can add the rose syrup or the food color to this slurry too.