Sweet curd) is a fermented sweet doi (yogurt) originating from the Bengal region of the Indian subcontinent[1] and common in the Indian states of West Bengal, Tripura, Assam's Barak Valley,[2] and in the nation of Bangladesh.

[5] Mishti doi is prepared by boiling milk until it is slightly thickened, sweetening it with sugar, either gura (brown sugar) or khejur gura (date molasses), and allowing the milk to ferment overnight.

[6] Earthenware is always used as the container for making mitha dahi because the gradual evaporation of water through its porous walls not only further thickens the yoghurt,[7] but also produces the right temperature for the growth of the culture.

Very often the yoghurt is delicately seasoned with a pinch of cardamom for fragrance.

Before the discovery of miracle drugs for typhoid, well-known alopathic physicians like Dr. B. C. Roy, Col. Denham White and Nilratan Sircar prescribed mishti doi for their patients which helps to accumulate Vitamin Bs.