The experiment consisted of creating an entangled pair of phonons sitting inside a bit of liquid that had been forced (via laser) to move very fast and then observing the action as one of the pair was pulled away as the liquid began to move faster than the speed of sound, while the other escaped—the fluid was a Bose-Enistein condensate of rubidium-87 atoms. After repeating the experiment 4,600 times Steinhauer became convinced that the particles were entangled, a necessity for a Hawking radiation analogue. His findings do not prove Hawking's theory to be true, of course, but they do appear to add a degree of credence that other researchers have thus far not been able to achieve.
Arxiv - Observation of thermal Hawking radiation and its entanglement in an analogue black hole (14 page pdf)
Nature Physics - Observation of quantum Hawking radiation and its entanglement in an analogue black hole
SOURCES- Arxiv, Nature Physics, Youtube, University of Waterloo, Phys.org