Preheat the oven to 160ºC. To a bowl, add the eggs and sweetener. Whisk with an electric whisk until thick, pale, and frothy (this should take about 5 minutes total).
Add the defatted almond flour, baking powder, and almond extract. Fold everything into the egg mixture.
Spray the silicon moulds with low-calorie cooking spray. Fill the egg moulds with the cake mixture (this made 10 in the mould we used, but your amount will depend on the shape and size of your mould). Do not fill completely to the top, leave a little room for the cakes to rise in the oven.
Bake for 20 minutes, until cooked through and golden. Take the cakes out of the oven and leave to cool in the silicone mould for 5 minutes, before carefully pushing them out onto a wire rack.
When the cakes have cooled completely, make your icing by combining the icing sugar with the water. Mix until smooth (you can add food colouring too if you like, we went with blue). Decorate the cakes with the icing, along with any sprinkles you fancy.