Place beetroot in a large saucepan over medium-high heat. Add milk. Cook, stirring occasionally, for 10-15 minutes or until beetroot become soft.
When 50% -60% of the milk has evaporated, add sugar and ghee (if using). Cook, stirring constantly, until the sugar dissolves.
Continue stirring until 90% of the milk has evaporated, and the halwa becomes very thick but not dry.
Stir ground cardamom into the halwa. Cook, stirring constantly, for another 5 minutes.
If you are adding roasted cashew nuts and raisins to the halwa, stir them into rhe halwa just before removing it from the heat and allow to heat through.
Garnish with more nuts of your choice if you like. Serve beetroot halwa hot or cold.