Although I don't read medieval Persian, my guess is that "burned vegetable oil" would be better translated as "mustard oil heated to its smoke point". Mustard o

Although I don't read medieval Persian, my guess is that "burned vegetable oil" would be better translated as "mustard oil heated to its smoke point". Mustard oil was (and still is) a common cooking oil in the region, and heating it to high temperature reduces the pungent taste.