I bake around 8 cakes twice a week. These are large celebration cakes in a professional oven. These have been made the same way for many years and occasionally the bake would be patchy as in the picture, but lately this has been happening a lot more often, maybe every 2 to 3 bakes. We have tried different people baking the cakes, different flour and different butter / margarine but so far none of these seem to have made any difference. Please can anyone tell me what causes the dense patches in cakes like the one below.
