Is it true that you smell burny toast when having a stroke? If so what is happening?

One of many symptoms. Odd smells, visions, and a multitude of other symptoms are all possible with a stroke. The type of symptoms you have depends on what part of the brain the stroke is affecting. If you are experiencing strange sensations, smells, weakness, loss of function, you should seek further care. Other brain pathology, and not just strokes, can also cause these symptoms.
Possibly. Detecting pungent or foul odors that aren't really there is called phantosmia while noticing an odor that seems distorted is dysosmia. These symptoms can occur with damage to the olfactory nerves from trauma, or infection such as sinusitis. Other causes are temporal lobe seizures, brain tumors, migraine headaches, stroke and parkinson's disease.