1. Grind the cashew nuts to a fine powder using a coffee grinder: make sure the cashew nuts are dry, and pulse to get a fine flour, stopping when the nuts start releasing the oils and turn to a paste. Set aside.
2. Add the sugar and water to a thick-bottomed saucepan and dissolve the sugar over low heat. Add the cashew flour, stirring continuously to combine well. Continue stirring until the mixture thickens and starts looking like a soft dough, pulling away from the sides. This may take around 6-10 minutes. It should be dry enough to not stick to your fingers. Remove from the heat.
3. Place the cashew dough on a clean work surface. Let cool slightly so that it is still hot but not too hot to touch. Add the crushed rose petals, ghee, and knead the dough lightly with your hands until it appears smooth. If the dough appears too dry or dense, add half a teaspoon of milk to soften the dough.
4. Place the dough on a lightly greased work surface. The dough should still be warm to touch. Using a rolling pin, gently roll out the dough to a 3-5mm thickness. Let it cool.
5. Use a sharp knife to cut the dough into squares or diamond shapes. Gently lift the kaju katli pieces and place on a dish, serve immediately or store in an airtight container.