Cooking things from packets

[BertieBotts]

Why does following the instructions never work? And how do other people magically know what the right cooking times/temperatures/etc are? Is it just trial and error?

(Yes I know nobody on mumsnet ever uses processed food... humour me for a moment, please )

like what? i can't say i've really had problems with any pre-prepared food, aside from my waitrose chips which took forever to cook

Well I have just had a bird's eye pie, cooked for 35 mins (packet said 30) and the pastry was still undercooked. Not sure what other things, because it was a while ago the last time it happened, but it was in a different oven, so it's not the cooker.

It depends on whether you have preheated your oven and on whether you use the correct shelf position for the cooking method (fan/combination etc). My oven manual tells me these things...but obviously I know nothing about pre-prepared food (other than the meals the takeaway deliver to my door)

Yes I had preheated it - for some reason there is no light to say when my oven is up to temperature but if you listen, you can very clearly hear that the gas stops hissing as loudly and becomes very quiet which I assume means it is up to temperature (usually takes about 10 mins I think) - but shelf position might be something, I had never thought about this before, I just assumed in oven = hot. Does anyone know about shelf positions?

I know gas ovens aren't as good as electric ones.....

FIL's oven seems to have temp fluctations and suffers from variable gas pressure or something.

....and that is about the extent of my gas cooker knowledge I'm afraid.

It could be a shelf problem you have.

If you want say 180, assume after pre-heating, that the middle shelf is 180.

And assume that the bottom shelf is 160, and the top is shelf is 200.

So middle is the right temp, top hotter, bottom colder.

good point about shelves.
I think if you have a fan oven that's supposed to overcome that problem, however I have a fan oven and the top is still hottest!