Put a large baking sheet into the freezer for 10 minutes. Using a melon baller, scoop balls of ice cream and place these on the baking sheet. Freeze for at least 1 hour or until firm.
Line a second baking sheet with baking parchment and place in the freezer for 15 minutes. Melt the plain chocolate in a heatproof bowl set over a pan of gently simmering water. Melt the milk chocolate in a separate bowl.
Using a metal spatula, transfer the ice cream scoops to the parchment-lined sheet. Spoon a little plain chocolate over one scoop so that most of it is coated.
Sprinkle immediately with chopped nuts, before the chocolate sets. Coat half the remaining scoops in the same way, sprinkling each one with nuts before the chocolate sets. Spoon the remaining plain chocolate over the remaining scoops.
Using a tsp, drizzle the milk chocolate over the choc-ices that are not topped with nuts. Freeze again until ready to serve.