Preheat the oven to 200C. Brush the madeleine tray with butter and lightly coat in plain flour, tapping out the excess.
Beat the eggs and sugar together until they're fully combined and frothy.
Whisk in the remaining ingredients, combining the flour little by little.
Leave the mixture for 20 minutes to stand. It will slightly thicken.
Pour into the madeleine tray, filling each one 2/3 of the way.
Bake for 8-12 minutes, I find 11 minutes the perfect time. You should expect them to have their characteristic 'hump' by minute 5 or so. Try not to open the oven whilst they're baking.
Transfer to a wire cooling tray and cover with icing sugar.
Enjoy! These are best eaten within an hour of baking (but good luck making them last that long)