Who read Jeremiah's scroll aloud to the king as he cut it up and burned it?

Answer: Jehudi

The king sent Jehudi to get the scroll from Elishama's chamber, and Jehudi read it while the king cut and burned it.

“Then the king sent Jehudi to get the scroll, and he took it from the chamber of Elishama the scribe. And Jehudi read it in the hearing of the king and all the officials who were standing beside him.”— Jeremiah 36:21 (BSB)