Hi, I have made Nigella's walnut and coffee cake four times, on the first occasion it was fabulous, however all subsequent bakes have sunk and were greasy. I have used correct size tins, ingredients at room temp and used fan/conventional ovens. Cakes placed in middle of the oven. I have used all in one and creaming method but both split. Would appreciate your advice. Thanks.
Nigella's Coffee And Walnut Layer Cake from KITCHEN) is similar to a Victoria sponge cake but has ground walnuts added to the cake batter. From the description we wonder if the walnuts are being ground for too long. The nuts are ground in a food processor with the sugar just until the nuts have been ground to a powder. If nuts are ground for too long then they will become oily and this could cause the cake batter to split and become greasy.
Grinding the nuts with the sugar does reduce the risk of the nuts becoming greasy, but it is still possible to grind them to the point where they release some oil. So if you are not sure we suggest using the pulse mode on a food processor and stopping as soon as the nuts look to be very finely chopped but the nut and sugar mixture is still dry and loose. If you are chopping the nuts by hand then use a sharp knife and try not to crush the nuts too much as you chop, as this will also release oils from the nuts. Also make sure that the cake is fully baked before you remove it from the oven, as if it is under baked it will sink as it cools. The sponge layers should be risen, firm to the touch, shrinking away from the sides of the tins slightly and a cake tester inserted into the centre of the sponges should come out clean.