"fluffy, totally cooked potato"
Thanks for reminding me about the fluffy potatoes. My mom noted that the baking a potato on a stick was a great treat. Extra delicious and very fluffy.
Are you sure it wasn't recycled solid fat, like butter that had been used for frying before, or some sort of Crisco - it would look yellow if it had been drained after use. I don't believe much in recycling cooking oil to be used again, but some people filter it. Mom used to re-use bacon fat.