Firstly, in a large bowl take 1 cup cornflour and 2 cups water.
whisk and mix well making sure there are no lumps. keep aside.

Now in a large kadai take 2 cups sugar and 1 cup water.

stir well until the sugar dissolves completely.

now get the sugar water to a boil. no need to attain string consistency.

keep stirring, and pour in prepared cornflour water.

Now pour in 1 tsp lemon juice and continue to mix. lemon is used to prevent sugar from crystalizing.

further, add 1 tbsp of ghee and continue to mix.

mix until the ghee is well absorbed.

keep adding ghee in batches until it absorbs completely.

once the mixture turns glossy, add ¼ tsp green food colour and mix well.
(You can add pistachio essence)
now add 2 tbsp roasted pistachio and 2 tbsp sunflower seeds.

Mix well making sure everything is well combined.

After 30 minutes, the mixture will turn super glossy.

Now add 2 tsp of more ghee and continue to stir until the mixture starts to release ghee.

Transfer the halwa mixture into the tray.

Sprinkle few chopped pistachio & sunflower seeds and level it up.

Rest for 30 minutes or until the halwa is set completely.

Finally, cut karachi halwa into pieces and enjoy for 2 weeks when refrigerated.