Boil water, sugar, and cardamom powder together in a pan until sugar dissolves.
In a separate pan, melt ghee, roast cashews and raisins until golden, and set aside.
Add semolina to remaining ghee and roast on low heat until golden brown and fragrant (about 8 minutes).
Slowly pour warm sugar syrup into roasted semolina while stirring continuously to prevent lumps.
Cook on low heat until halwa thickens and leaves pan sides; garnish with roasted nuts.