Rinse and dry the mushrooms well. Remove the stems from the mushroom. And chop the stems and keep aside.
In a bowl mix 2 tbsp of olive oil, add 1 tsp chili flakes, and salt. Using a brush coat the olive oil-chilli mixture inside and outside the mushrooms.
For stuffing
In a heated pan, add the remaining oil, spring onions, red peppers, mushrooms stems, chili flakes, garlic powder, and salt and fry on high heat for 5 minutes. Switch it off.
Add the panko bread crumbs. Transfer to the processor and add cheese and process chunky. Do not make it as a paste.
Fill this stuffing into each mushroom. Place the mushrooms onto a grill rack above a baking sheet. Bake for 15 minutes.
Notes
If you have chopped your peppers and mushroom stems finely, you can avoid a food processor.
If using a processor, make sure you don't make them into a paste.