I've never had this in a BIR (!) but I enjoyed it, so if anyone tries it feedback would be welcome.
4 TBSP oil (at least)
1 TBSP G/G paste
1/2 tsp asafoetida
quarter onion sliced medium fine
2 tsp tomato puree (watered down with 1TBSP water)
1 TBSP methi
3 tsp spice mix (Bruce Edward's, 8 coriander : 7 turmeric : 5 cumin : 4 curry powder)
1/2 tsp garam masala
1 tsp chilli powder
200g pureed spinach
50g chopped spinach
1/2 chicken stock cube
1/2 tsp salt (or to taste)
2 tsp sugar (or to taste)
4 TBSP evaporated milk or single cream
25g butter
1 portion of pre-cooked chicken
enough pre heated base sauce for 1 portion + half as much more water (or as required, use your judgement)
1 TBSP coriander leaf
Heat oil on high heat, add G/G paste and stir occasionally.
before the G/G paste browns add onion slices and cook on until G/g paste is done.
add asafoetida and stir for a few seconds.
add spices, methi, salt and sugar, and cook on until you get the toffee smell, then quickly add the tomato puree and stir for a few seconds until it thickens again.
Add a ladle of base and cook this down, stirring all the time, until it thickens.
Add the remainder of the base, the two types of spinach, the stock cube, and the pre cooked chicken. There should be a lot of liquid at this point because you want to boil this down on highish heat to concentrate the flavour.
When the sauce is nearly reduced to a single portion add the cream and coriander leaf and continue to cook at a slightly lower heat until you have it down to a single portion.
Turn the heat off and add the butter. Stir around until the butter is just incorporated into the sauce.
Serve sprinkled with roughly chopped coriander leaf.
I don't believe any of the ingredients (except perhaps the cream) are optional. I researched the authentic saag recipes and then made it BIR style.