As another reviewer noted, this is not like "restaurant style" Murgh Makhni. On the other hand, authentic Indian food is seldom like American-style "Indian" restaurant food. Thick gravy is made in restaurants by the addition of cornstarch or other thickener. No Indian cook I know does so.
While the recipe calls for two onions, the size of onions varies greatly - up to grapefruit size. I'd suggest using onions to taste, especially since people vary wildly in how well they like onions.
I think the suggested size for the chicken is too big, I'd go for about an inch cubes and then it'll cook more quickly too. Prep time is about right.
Somebody complained about the ingredients being incorrect - that again is a matter of taste. There is no one recipe for any Indian dish, although some vary less than others. India's a big place. I've seen simpler recipes and I've seen more complicated - Indian cooks are typically a LOT more inventive than most American's I know. This one is typical of the dish as served in many, though not all, Indian homes. The bell pepper is not so typical in India, but many Indian cooks use it stateside because of the ready availability here.