Cut the tops off the king oyster mushrooms and use for another dish. Cut the stems into 2-3cm thick slices. Cut some cross lines on one side.
Place oil in a frying pan over medium heat and place the king oyster mushrooms in. Fry one side until slightly seared and then turn over the fry the other side until lightly seared.
Cook the soba noodles according to packet directions, drain and divide amongst serving bowls. Top the noodles with seared mushrooms, pickled shiitake mushrooms and spring onions. To serve pour hot dashi stock amongst the bowls and serve immediately.