Scatter the berries into medium remekins or a large, shallow heatproof dish, preferably in a single layer. Sprinkle with the lemon zest, cover and chill until ready to serve.
Meanwhile, break up the chocolate into a small heatproof bowl. Heat the cream in a pan until almost boiling, then pour onto the chocolate. Leave for 3 mins, then stir slowly until dissolved. Allow to cool to room temperature until thickened.
To serve, heat the grill for a good 5 mins until glowing hot. Spoon the chocolate cream over the berries, sprinkle over the icing sugar and place under the grill. Grill for 2-3 mins until the sauce begins to brown, turning the dish if necessary. Remove and serve immediately.