I have totally fallen in love with this cake recipe. It is great for people on grain-free and low-fat diets (just don't put the butter cream frosting on top if you want to avoid fat....yeah, that's all fat.). This recipe would work perfectly for a more traditional sponge cake, a sponge roll, trifles, tiramisu...the list goes on. It's so good. I've been dying to find more uses for potato flour, especially since it is so close to St. Patrick's day! The homemade butter cream frosting is tinted green with spinach. It looks really beautiful - light green with darker green speckles - and you can't taste the spinach at all.
The recipe for the sponge cake comes from the website GrainFreeLiving.com. The leavening for this cake comes primarily from the air that is beaten into the eggs, and partly from the baking soda. It should be noted that the potato flour sponge cake recipe is in metric measurements. 1 cup is 250ml which is slightly larger than the imperial 1 cup of an 8 oz measure.
3/4 cup sugar
3/4 cup potato flour
1/4 cup arrowroot/tapioca flour
1/2 tsp baking soda
1 tsp cream of tarter
Preheat the oven to 340F (170C) and get your cupcake tins or cake tins ready. This recipe made 12 cupcakes for me, but I overfilled the tins a bit - it should probably be more like 14-16 cupcakes. It is vital to get the tins and oven ready beforehand because the chemical reaction of the leavening ingredients begins as soon as the batter is combined. If you wait to long to get it into the oven the chemical reaction will be over and you won't end up with the right texture.
Separate the eggs and reserve the yolks in a small bowl, place the egg whites in a large mixing bowl. Beat the egg whites until they are stiff. I beat my eggs until they had soft peaks, but I think the recipe would have come out better if I had been a bit more patient. Gradually add the sugar to the eggs until the mixture is creamy and thick, the beat in the egg yolks one by one.
Sift together the remaining dry ingredients (potato flour, arrowroot, baking soda, cream of tarter and salt). Gently fold the dry ingredients into the beaten egg and sugar mix until fully incorporated, being careful not to over mix.
Gently scoop into the cupcake tin, filling about 2/3 of the tin. (I overfilled mine. Whoops.) Bake in the oven for 13-15 minutes. If making a cake instead of cupcakes it should be 15-20 minutes. When the cupcakes are done they will be starting to turn a light golden color, and a toothpick inserted in the center will come out clean.
Spinach Green Butter Cream Frosting
1 cup spinach, steamed and drained
1/2 cup butter, softened
3 cups powdered sugar (about 1lb)
1 tsp. vanilla
Steam and drain the spinach, then place it in a food processor and puree it until smooth. Cream the butter and sugar together in a large bowl, add the vanilla and spinach and blend thoroughly. If the mixture is to moist add more powdered sugar. Should make enough to frost one large cake, or one batch of cupcakes.