Place the orange zest, eggs and sugar in the bowl of an electric mixer. Using the whisk attachment, whisk for 5 minutes on medium-high or until tripled in volume. Sieve over the flour and baking powder and gently fold in. Pout in the melted butter in 4 additions, gently mixing between each addition. Cover bowl with cling film and refrigerate for at least 4 hours or overnight.
Preheat the oven to 180°C. Lightly grease two 12-hole Madeleine pans. Divide the batter between the pans by gently spooning about a tablespoon of the mixture into each shell. Ensure you don't spread the mixture out, although it may seem firm, it will spread during the bake. I didn't bake all of mine at once so their sizes weren't all that even, but it didn't matter too much and just affected the shape a little. Bake for approximately 10 minutes or until risen and golden. Gently remove the Madeleines from the pan and leave to cool slightly.
Meanwhile make the icing. Mix all the ingredients together until all combined. It should be thick but a pourable consistency and a pale green colour.
To finish the Madeleines, dip the shell side of the Madeleines in the icing and hold for a few seconds to allow excess to drip off. Sprinkle a little of the Genmaicha over the iced Madeleines and allow to set for a few minutes. Repeat with remaining Madeleines and serve.
