Preheat the oven to 400 F. Grease 2 Madeleine tins and dust them with flour, tapping out any excess.
Sift the flour and cornflour together, then stir in the ground almonds and set aside. Whip the egg yolks with 3 Tbsp of the sugar until thick and pale and they hold a ribbon when the beaters are lifted, then beat in the almond extract. In a separate bowl, whip the egg whites until foamy, then slowly add the remaining 6 Tbsp of sugar and continue whipping until the whites hold a medium peak when the beaters are lifted.
Fold the whites into the yolk mixtures using a whisk, then fold in the flour until just incorporated. Spoon the batter into the prepared Madeleine tins so they are almost full. Bake for about 8 minutes, until the Madeleines are an even golden brown. Allow them to cool completely before removing them from the tins.
For dipping, whisk the icing sugar and 1 Tbsp milk together, adding more milk if needed to make a thin icing. Dip each Madeleine halfway into the icing and then dip it into the coconut. Let the Madeleines set for an hour, then store in an airtight container until ready to serve.
The Madeleines will keep in an airtight container for up to 4 days.