In a bowl, combine all ingredients for sauce. Set aside until ready to assemble.
In a separate bowl, combine meat and then fold in spices, shitake powder and Worcestershire sauce. Divide into thin patties.
Cook patties over medium-high heat in a cast iron skillet or griddle top. Layer 2 patties with a slice of cheese between them. Top with shaved onion and bread and butter pickles. Serve on a potato roll burger.