Although I have made plenty of different base gravies, this is a very good go-to in my opinion as it allows the ingredients in the curry preparation to speak for themselves. I believe the secret ingredient in *some* restaurants is MSG in some form (even if they don't, or won't, tell you this). It is prominent on the shelves of Indian supermarkets, is the major component of other condiments known to be used in base gravy recipes (Maggi seasoning for example) and it lifts all the flavours you put in your curry. Try it and see what you think.
The volume of water isn't all that important in the IP, as long as the resulting blend is split into 6 equal portions. This is a well-seasoned gravy so you might want to cut the salt content in your curries, according to taste.
I have acquired some recipes from a local 'posh' restaurant, which I'll post at some point. The chicken tikka is very interesting but there's also a nice desi lamb recipe, which is simpler than it sounds - although they use mustard oil, so it's hard to replicate the taste exactly without this.
INGREDIENTS:-
1kg onions (no need to chop)
60g garlic paste or whole garlic cloves
60g chopped ginger or ginger paste (or Lidl style jarred ginger strips work fine, as the vinegar cooks out)
1/2 small green pepper
420ml rapeseed oil - cold pressed has a bit more depth if you have that available
2 tsp salt
3/4 tsp msg powder
1 tsp sugar
1 very small carrot
4.5 tsps turmeric
4.5tsp bold cumin seeds
4.5tsps coriander seeds, ground coarsely in pestle and mortar
400ml water
2 tbsp tomato puree
Put ingredients in instant pot, stir and set to 25 mins. Allow to natural release.
Blend with a stick blender, split into 6 equal portions to be diluted to consistency of whole milk for each curry.