Cut off mushrooms legs.
Chop mushroom legs and onion, mix, add oat flakes and fry the mixture in olive oil.
Slice tomatoes and pepper, mix with onion mixture, add greens, salt, pepper and stir up.
Stuff mushrooms caps with prepared mass, season with cheese.
Bake caps for 15 minutes over 390°F.
When serving, top the starter with greens.
