Guys-have a look here, i have tried these and you can get high temps in a domestic oven.
You can get them in the UK but sadly I lost mine when my (now ex)wife cleared the house out while I was at work!
http://www.romertopfonline.com/clay-bakers/
Hope this helps
Phil

Axe- I hear what you say,I'm just thinking that in a BIR environment, the sauce is always on the stove,and therefore always cooking-the base sauce recipes one here are probably very authentic to a point, but they seem to be cooked fairly quickly,from what I've read then they get portioned up and chucked in the freezer, whereas the BIR version, would be stewing a lot longer and therefore releasing its sugars slowly.
Having said that-what do I know!, I'm a relative newbie and I've never worked In a BIR,and whilst I think the base sauces on here are authentic, I'm guessing that they get cooked a lot longer in a restuarant situation- thus releasing those magical sugars and taking away the boiled onion taste.
Once again- love the feedback and great advice on here!
Phil

Phil-I was coing to add the caremelised onions instead of raw onions to the base sauce recipe-I made a dopiaza the other night using caramelised onions and it was superb-I use bunjjarra paste in my curries too- which are in effect spiced caremelised onionns
phil

I too have been thinking about the sweetness thing that razor mentions_ I cant help felling that boiling onions for an hour or so which is what most base sauces call for will result in a slightly bitter base, unless sugar is added as an extra.
Infact the base sauces I've made have always had an underlying 'boiled onion' flavour which isn't particularly nice in my opinion and only gets lost by generous use of spices in finished curry.
I've done a bit of reading up on the chemistry of onions(given that onions are the major constituent in base sauces)and onions have their own sugars- you just have to cook them right to release them.
For my next base sauce I'm going to caramelise the onions first by slow frying for around 40 Min's (probably with garlic too as this is a form of onion) then add caramelised
onions to the remaining base ingredients will then slow cook overnight in crockpot on low.
What I'm hoping to achieve is the removal of the boiled onion flavour and addition of the onions natural sweetness-what are your thoughts on this?
Phil

From what I've seen on 'posh' cooking sites cassia bark is regarded as poor mans cinnamon- its certainly a lot cheaper, I accidentally bought a bag last week- it was marked as Cinnamon sticks- only when i got it home did i notice  in very small letters it said Chinese cinnamon sticks( the Chinese bit was in very small letters) and it turned out to be cassia bark.
I don't think theres a huge diff between the two personally- especially in a curry, where theres all sorts of other spices fighting for competition.
As for weighing it- well i just would guess,its not as powerful as proper cinnamon,have a guess is what i usually do!