Not knowing what recipe, instructions or ingredients you used, it’s impossible to know why went wrong.
In the UK, what they call a sponge is actually a pound cake, not a sponge cake at all.
A sponge cake does not contain any fat, it is leavened with whipped a egg whites.
A shortened cake is made by creaming butter and sugar is leavened with Chemical leavening (Baking powder and/or baking soda) and using mechanical leavening (creaming butter and sugar). This is more commonly called a butter cake. A pound cake (equal parts by weight of butter, sugar, egg, and flour) is in this category. The British Victoria “Sponge” and almost all “sponge” cakes in the UK are these pound cakes.
Genoise is a Italian sponge cake leavened with whipped egg, the difference is after the whipped eggs and flour are mixed, clarified butter is added to the batter.
Most recipes for shortened cakes incorrectly instruct using “room temperature” butter. When butter is creamed at the wrong temperature it loses its plasticity. As I mentioned above creamy butter and sugar is mechanical leavening, so when it loses its plasticity it cannot expand and hold the gas bubbles created by the baking powder/soda. when you don’t have affective expansion of the butter you don’t have good fries in the cake.
The correct temperature for creaming butter is 65°F (18°C). Look up Stella Parks Article on Serious Eats creaming butter. parks discusses creamy butter in relation to cookies, but it applies to all baking.
Where you live and the recipe you used also makes a difference. ingredients are significantly different by country. The flour in the Canada is very high in protein compare to US and Europe. UK plain flour is equivalent to US and Canadian pastry flour, not all purpose flour. So if you are in the UK and use a US or Canadian recipe that calls for pain flour, you need a stronger flour. UK eggs are significantly larger than US and Canadian eggs, so if you a recipe from an American or Canadian author, you have to use medium eggs, not large eggs. American and Canadian butter has lower butterfat than European butter. A lot of American flours are bleached, so any recipe with bleached flour will absorb less liquid. So if you used umbleached flour, your cake won’t rise as much because unbleached flour will absorb more liquid.
Are you starting to see why your not providing information makes it impossible to help you?
