Sponge cake rising then flopping - help!

[catski]

Well, okay, it's an almond cake but it's the fourth time I've tried this and I'm going mad.

The recipe I'm using is for a six inch round tin:
150 g butter (room temp)
150g sugar (can't get caster sugar where I live)
112g plain flour (can't get self raising flour either)
38g ground almond
1.375 teaspoons baking powder (or 7g)
3 eggs (I measure them and made sure they were 150g)
.5 teaspoon vanilla extract
couple of drops of almond essence

I am using a kitchenaid mixer and the paddle attachment and am beating butter and sugar until light and fluffy, adding egs one at a time and beating well after each addition, sifting the flour in and then mixing it in using the lowest speed, adding vanilla and almond extract and then putting in the oven.

Am baking at 160 degrees. I have an electric fan oven, but with option to turn the fan off and use it as a conventional oven, which I am doing. Oven has an internal thermometer so I know it's 160 when I put the cake in. Baking time says 50 minutes, but I'm not opening the door until after an hour (first time I peeked at 50 minutes and thought that was the problem). Same thing happens every time - it rises spectacularly until about 45 minutes and then flops dramatically. Not just a little bit sad, massively flopped and unsalvageable.

What am I doing wrong?

I don't know, but hopefully slubberdegullion will be along shortly to advise you. She knows all about cakes. Or nickelbabe, if slubber's not available.

i suggest cooking it in a hotter oven

180 with fan.

also when you are going to get it out LISTEN to it. (get your ear close) if you can hear a bubbly poppy fizzy noise then its not cooked enough and needs longer

Thanks nannyl. I will try that. I should also have added that I was using those bake even strips from Wilton, although when I do a madeira recipe I never have the sinkage problem.

Could be too much baking powder? I think I read somewhere that too much makes cakes rise quickly, but then rise isn't sustained for long enough, and the cake flops. Something like that anyway. If I'm talking rubbish, someone correct me.
Is it rising just in the middle, or evenly?

7 g baking powder is a dose for 500g of flour, so maybe that's the problem? It raises too much and then flops.

mm yes.

The recipe I just did was for half a teaspoon of baking powder with 250g flour.

The egg in the recipe sets the matrix of the risen flour and sugar so maybe your cake is zooming up too fast as the others have said before the egg has had a chance to cook and set yet?

Oh wow, that's a huge difference in baking powder. Yes, it stands to reason doesn't it that the cake is rising too fast before the cake has a chance to set, which must mean either too much baking powder or oven too hot (doesn't it?). Might invest in an oven thermometer (although it does have an internal one) and try less baking powder, and if that doesn't work bite the bullet and pay an extortionate sum for some self raising flour at the English shop!

I'd also add the vanilla and almond essence with the last egg, so you have less mixing once you've added the flour, keep more air in the mixture.
I substitute self raising flour with 250g of flour mixed with one tsp baking powder and 1/2 tsp bicarb of soda.

I have great problems making cakes at work. I've some things sussed, such as lowering the temperature a bit from what it say, as the work oven seems to get too hot. Also I tend to use either a loaf tin, or a deep sided rectangular baking tray. Round tins just never seem to work.

Just had a look at my great aunt's cookery book and the reasons for sinking cakes could be:

Oven too hot.
(I read somewhere that ovens are often hotter than the regulo says).

Too much raising agent baking powder or bicarb soda.

Raising agent past its use by date
Raising agents should be stored in an airtight tin, if it doesn't effervesce if you put some grains on the tip of your tongue it has lost its raising properties and should be thrown away.

Working the mixture too much after the flour has been added can cause heaviness. Fold it in gently with a knife in a figure of eight pattern until just mixed.

(I go with the too much baking powder theory)

Nannynick, are all round baking tins a problem for you or do you always try with the same one? It might be just that one round tin that's no good. And what exactly goes wrong?