Pour the sugar into a metal container, melt it on low heat to a golden brown caramel while stirring nonstop.
To it pour in the boiling milk and stir until dissolved. Remove from the heat and add the raisins, juice and zest of the orange.
In another container, melt the butter and braise the semolina in it until golden. Pour the milk into it and boil 5-6 min. on low heat while stirring nonstop.
Pour the mixture into a suitable tray, even it out and leave it aside until fully cooled
Cut your ready halva into the desired sizes and shapes of the pieces and sprinkle with ground walnuts.