Heat the oven to 190°C.
Take the stems out of the mushrooms and finely chop them.
Finely chop the red pepper, walnuts, chilli and onion.
Heat the vegetable oil in a wok and stir-fry the onion, chilli and pepper for 3-5 minutes. Add the grated garlic and ginger, then the walnuts. Stir-fry for 30 seconds, then add the soy sauce and ground peppercorn. Let it sizzle for a minute, then turn off the heat.
Let it cool a bit, then stir in the chopped coriander and sesame oil.
Arrange the mushroom caps on a baking tray.
Spoon the mixture into each mushroom cap.
Bake the mushroom for approx. 15 minutes until golden.
Serve warm.