SakaMai’s wagyu katsu sandwich, as well as our umami butter, gets some love from Eater:
"Back in New York, SakaMai pairs its steak with an “umami butter,” which contains chicken fat and koji (the mold used to make sake)"
See the full article here:
https://www.eater.com/2018/1/24/16921498/best-wagyu-katsu-sandwich-tokyo-nyc-boston