For the praline:
Heat the sugar in a broad non-stick pan and cook on a medium flame for 5 to7 minutes or till the sugar melts, while stirring continuously. Remove from the flame, add the cashewnuts and butter and mix well. Spread the mixture on a greased flat surface and allow it to cool and harden. Scrape it out using a palate knife and coarsely powder it using a mortar-pestle. Keep aside.
For the ice-cream:
Combine all the ingredients except the butterscotch essence and whisk together so that no lumps remain. Bring to a boil in a non-stick pan and simmer for 7 minutes, while stirring continuously. Cool completely, add the butterscotch essence and mix well. Pour the mixture into a shallow aluminium container. Cover with an aluminium foil and freeze for 6 hours or till semi-set. Remove the semi-set ice-cream from the freezer and transfer it in a mixer and blend till smooth.
Add the prepared praline and mix well. Transfer the mixture back into the same aluminium shallow container. Cover with an aluminium foil and freeze for approx. 10 hours or till set.
Scoop and serve.