Preheat the oven to 190°C, fan 170°C, gas 5. Line a 12-hole fairy cake tin with fairy cake paper cases.
In a mixing bowl, make up the sponge mix according to pack instructions with the egg and 75ml cold water, beating with a hand-held electric whisk for 3 minutes. Lightly stir through all but 12 of the raspberries and all of the nectarine slices, then spoon the mixture evenly between the paper cases.
Bake in the oven for 20 minutes, until golden and just firm to the touch. While the cakes are still warm, brush the tops with honey and top each with a raspberry. Dust with icing sugar and serve either warm or cold.
Cook's tip: you could use other soft fruits in these: try 125g blueberries and a chopped plum, or 125g strawberries and half a chopped banana.