Place the mushrooms in a food processor in small batches, the mushrooms should just barely cover the blades. Pulse 2-4 times at about 1/2 second intervals to create pieces that average 1/4 - 1/2" wide. Remove the mushrooms to a separate mixing bowl, sift out any extra large pieces and return them to the processor. Repeat with more batches until all the mushrooms have been processed

Combine all the dry spices in one bowl and the soy sauce and vinegar in another

Heat the olive oil in a large pan on medium-high until shimmering. Add the mushrooms, season with the spices and the soy sauce, the stir fry for 3-4 minutes, stirring constantly

Drain the mushrooms in a fine sieve, return to the pan and sprinkle with the corn starch, then stir to fully coat