Sponge cake sunk in middle.

[Humphriescushion]

Got a shiny, swanky stand mixer ( not a kitchen aid but near enough for me), for christmas. Made a sponge cake using the all in one method - this is what I also did with my old kenwood processor with no problems.

Cake sank the middle and was not that good overall. This is a tried and trusted recipe and I dont normally have any probelms with this. I did not open the oven door either.

What did I do wrong? Does it need less baking powder because more air is going in? Did I mix it for too long ( dont think I did - seemed correct consistency and was only beating for a v short time). Can I not do this method with a stand mixer?
Any suggestions appreciated since feeling a bit downhearted that I have spent a lot of money and my old kenwood is better.
It is an electrolux assistent if that helps - but seems identical to the kitchenaid - apart from the price

Sunk in the middle is normally an oven issue or a something missed out of the recipe issue. Could someone have opened the oven before the cake was cooked? Is your oven heating properly? Did you add all the eggs/flour (I know I've forgotten an egg or been an oz or 2 of flour short due to scale issues)

I've never had collapsing issue due to a mixer and I use lots of them, including the one you have, in various kitchens.

Oven too hot!

Whenever I've had a cake disaster its usually been because I added too much baking powder or the oven has been too hot - in both cases the cake whooshes up really quickly then sinks back down. The first cake I made with my Kenwood was very disappointing, a quite solid, almost chewy texture - I put that down to me playing about with the mixer and beating it for too long and over working the flour.

Ok that is reassuring Gherkin. Fairly sure everything added and noone opened the door. I was in the kitchen the whole time.

Cooked it at 160 fan as per recipe - dont think there is anything wrong with my oven - Yorkie, but I have another oven so will try that oven next time.

The mixture looked fine so hopefully you are right and it is the oven temp, maybe too hot for this recipe.

Thanks Nanny - yes, i feel that there was maybe too much baking powder. The recipe say self raising flour and a teaspoon and a half of baking powder. Though I am fairly sure this recipe has worked before.

Sinking could be due to:

Opening oven door during baking
Over beating mixture
Adding eggs too soon instead of one at a time
Adding flour too quickly instead of folding in slowly
Oven being too low
Too much cake mixture for the size of pan
and yes, too much raising agent.

Thanks Maryberry!
Oven too low to add to the list? Nooooooo
Hope it is not overbeating since i I wont be sure the next time - dont think I beat it too much, was just till it looked right. I chucked everything in together so should not be the other things - unless you cant use the all in one method with a stand mixer ( which I always use).

I always use the all in one method and I always use my stand mixer.

Mary Berry herself is a strong advocate of the all in one method and I've seen her put it to use in a kitchen aid on the bakeoff masterclasses.
I would say too much raising agent or oven problem. I only use about half a teaspoon of baking powder if I'm doing a 3 egg basic Victoria sponge and I get a lovely rise everytime.

thanks Formerly. By chance I am watching the bake off final and they did a sponge using this method. They ovens were at 180 though not 160 so will try again, with less raising agent and a hotter oven.
Thanks all. you have reassured me that it will work!