Chopped onions and tomatoes form the base of Yellow gravy. This gravy is typically used in Indian cuisine and is characterized by its use of onions and tomatoes, along with other spices.
- Brown gravy is made by roasting onions and tomatoes to a darker color, which is not the base for yellow gravy.
- Makhani gravy is rich and creamy, made with tomatoes, cream, and butter, which does not match the base described.
- White gravy is typically made with a milk or yogurt base and does not involve chopped onions and tomatoes.
Thus, the correct answer is Yellow gravy.