i got reminded of this post and realised i've pretty much settled on technique - unless anyone has any further savey tips that is.
stage 1 - hot frying in oil - unchanged to that detailed earlier in this post
http://www.curry-recipes.co.uk/curry/index.php?topic=1283.msg30817#msg30817stage 2 - spice emulsification (heat on full)
the what - add all of: spices, salt, chilli, tom puree/water, small amount base sauce ~ 1/2 ladle or 1 chef spoon
the how - pan off the heat, all added in one go, pan returned to the heat, 1 off good stir to ensure ingredient's are mixed, fry at high temp without stirring.
end point - the mixture is almost dried out around the edge of the pan and starts to crater across the surface. this is a difficult point to judge and u need to practise as it's easy to burn. it's not necessary to over cook - a little scrap with your spoon at the base of the pan rim gives a good indication.
stage 3 - evap off (heat on full or simmer*) (*to minimise splatter)
the what - add any of: base, fresh coriander, fresh tomato, passata, onion paste, coconut block/flour, evaporated milk/cream etc
the how - the pan can be on or off the heat, all are added in one go, 1 off real good stir (sideways and circular) needed to ensure the emulsified spices are fully mixed into the base, stir everynow and then 1st sideways then circular to clean the rim (frequent stirring not needed).
end point - the mixture is condensed to the the required consistency. typically starts to crater.
for me typical cooking times for 1 off 200ml finished portion are: stage 1 - 30sec, stage 2 - 1 min, stage 3 - 3 min. the times depend on your cooker, the amount of ingredient and the thinness of the base