Insert a cocktail stick into each grape, and place in the freezer for 1 hour.
Just before taking them out of the freezer, melt the chocolate and crush the nuts.
Remove the grapes from the freezer and dunk each one carefully into a bowl with the melted chocolate, followed by a bowl with the nuts. This will be easiest to do while the melted chocolate is still warm.
Pop in the freezer for 30 minutes or so to set. These will keep well in the freezer for up to a week.