This sponge cake was designed to be used as a layer in a more elaborate dessert. By itself the cake tends to be dry, it can be easily transformed with a little whipped cream, a butterscotch schnapps topping etc. Pictured above Speckled sponge with chocolate peanut butter icing.
Ingredients
165 g Potato starch*
130 g Caster sugar
6 Eggs (700 g/dozen)#
1 tsp Cream of tartar
1/2 tsp Bicarb of soda
75 g Dark chocolate (grated)
extra potato starch
* For more information on making sponges & the use of different starches refer to Sponge Basics.
# If using home grown eggs pick 6 medium sized eggs.
Method
If you keep your eggs in the fridge 1/2 fill the kitchen sink with hot tap water. Put the eggs in the hot tap water for 10 mins. If you keep your eggs at room temperature warm the eggs up by placing them in a dish of warm water (slightly hotter than 37 C).
Turn oven on to 175 C.
Sift together the starch, cream of tartar & bicarb three times into a mixing bowl.
Grate the chocolate & set it aside.
Grease two 20 cm cake tins. I use an oil spray. Put a ~heaped tablespoon of the extra potato starch into the cake tins. Coat the sides of the cake tin with the starch by rolling the tin around. Bang the tin on the bench to loosen off excess starch. Discard the excess starch.
Cut out two circles of baking paper to put on the bottom of the tin.
The yolks & whites will be whisked/beaten separately; you will need two mixing bowls. If you have two bowls for your stand mixer use those. If you have one beat the yolks first in the mixing bowl, transfer it to the bowl containing the sifted starch & then wash the mixing bowl for whisking the whites.
Measure out 80 g of sugar into the mixing bowl for the yolks. Put the remaining sugar into the bowl/container (not plastic) for the whites.
Separate 5 of the eggs. Put the yolks in with the 80 g of sugar & the whites in with the 50 g of sugar.
Put the last whole egg in with the yolks & sugar.
Beat the egg yolks & sugar for ~9 mins until the ribbon stage has been reached.
While the yolks are beating stir the egg white & sugar mix to help dissolve the sugar. I usually rest this mixing bowl on top of the hot tap water to help the sugar dissolve.
If using the same mixing bowl to whisk the egg whites as the one used for the yolks, transfer the yolk mix to the mixing bowl containing the sifted starch. Wash & dry the mixing bowl before putting in the egg whites & sugar mix.
Whisk the egg whites & sugar for 1 1/2 - 2 mins until stiff peaks form. The length of time to whisk the whites will depend on your mixer & the speed you are using. 2 mins at max speed in my KitchenAid is too long. It is not a disaster if the egg whites are slightly over whipped it just takes a little longer to fold into the yolk mix.
Fold in the sifted starch mix to the yolk mix. To fold put a spatula/scrapper into the centre of the bowl & push it down through the mix until it reaches the bottom of the bowl. Bring the spatula toward you all the time scrapping the bottom of the bowl. When the spatula is at the edge of the bowl bring it up out of the mix & with a twist of your hand (90 - 180 degree clockwise turn if right handed) turn the spatula over. The mix that was on top of the spatula will now fall back into the middle of the mix. Rotate the bowl clockwise with your left hand while repeating the spatula movement. Ensure the mix has a uniform consistency before proceeding.
Fold the grated chocolate into yolk mix. The chocolate will deflate the mixture a little.
Fold in the whisked whites to the yolk mixture using the technique described above. I usually fold it in without "loosening" the yolk mixture. "Loosening" the yolk mixture should make it easier to fold in the remaining whisked whites. The yolk mix can be "loosened" by adding up to 1/4 of the whisked whites & folding this in. The remainder of the whisked egg whites are then added & folded in.
Transfer the sponge batter to the two cake tins. Avoid putting the mix on the sides of the tin.
Put the tins in the oven & bake at 175 C for approximately 18 - 20 mins. The time required will depend on your oven. The sponge cakes are ready when the cakes start to leave the sides of the tin. I usually check them at 18 mins & depending what they look like leave them in the oven for another 1 - 2 mins. Another check is to gently press the centre of the cake, if there is no resistance the cake needs longer.
Before the cakes come out of the oven put baking paper on two cooling racks. Bring the cakes out of the oven & allow to cool briefly before removing the cake from the tin. To remove the sponge from the tin gently invert the tin over the baking paper. If the sponge doesn't come out, gently run a knife around the edges of the sponge & invert the tin again.
Allow to cool. Peel off the baking paper & invert the cake.
The sponge is now ready to be filled/iced/soaked & then eaten.