I don't use duck eggs but my grandmother always made a mean duck egg sponge cake. Legend has it that duck eggs produce the best sponges as they can whip up voluminously and the taste is richer and yet it rises much lighter.
An Original Recipe by Not Quite Nigella
These tips are essential for such a delicate cake and made the world of difference for us:
Tips:
•Use Duck Eggs if available
•Eggs must be at room temperature (for maximum volume when beating)
•Sift the dry ingredients together at a height using a fine sieve tapping the side of the sieve with the heel of your hand (instead of pressing the flour down through the sieve with a spoon)
•Ensure that the egg and sugar mixture is at least 3 times the original volume. It will take about 8-10 minutes.
•It’s a race against time once you add the dry ingredients to the egg so if you have someone to Sift the flour mixture into the egg mixture while you fold the mixture that is ideal. We got ours in the oven in about 2 minutes and we could see that as the time went on, the mixture started to fall
•Fold in the dry ingredients using a large metal spoon in an up, down and over movement.
•Lightly butter and flour the tin
Ingredients:
•4 Duck eggs (medium sized 420g are fine) or 5 large chicken eggs at room temperature
•2/3 cup caster/superfine sugar
•3/4 cup plain flour
•1/3 cup custard powder
•2 teaspoons baking powder
•A little butter and flour to grease the tins
•2 sponge tins or 2 spring form tines in the same size
Filling:
•300ml cream
•1/4 cup icing sugar
•60grams jam of your choice
•2 tablespoons icing sugar extra for dusting
1. Arrange oven rack so that it sits in the centre of the oven. Preheat oven to 180C/350F. Grease pans with butter and sift flour over butter and shake out excess flour. Whisk eggs and sugar on a medium high setting (I used setting #6 on the Kitchenaid) for 8-10 minutes until it has turned very pale and very thick and has increased in volume to at least 3 times its original volume.
2. Meanwhile, sift the flour and custard powder three times. Each time do it at a bit of a height and tap the side of the sieve with the heel of your hand or use your wrist to shake it back and forth (rather than pressing down on the flour with a spoon).
3. When the egg mixture is ready, ensure that the oven is at the correct temperature. Have everything ready as the timing is crucial now. Sift the flour into the mixture while someone else folds the mixture underneath. This helps to avoid the lumps. Use the up, down and under folding motion (do not stir). It folds easily and should be able to be incorporated easily. Quickly spoon it into the tins and bake in the center row of the oven and bake for 15-20 minutes. It should spring back slightly when touched and the edges should pull back from the tin.
4. Cool in the tins for 5 minutes and then remove from the tin gently and cool on a wire rack.
5. Beat cream with icing sugar until stiffish and spread this on one cake half (the heavier or less photogenic one is best). I like to smooth the sides with an angled palette knife for a smoother look. Spoon jam on top and place the other cake round on top and sift icing sugar on top.
and place the other cake round on top and sift icing sugar on top.
Recipe
Found here