Remove the stems from the button mushrooms and clean them gently under running water.

Finely mince the chicken breast.

Finely chop the onion and bell pepper.

Combine the minced chicken, onion, and bell pepper in a bowl. Add a pinch of black pepper for seasoning.

Stuff the mushroom caps with the prepared mixture.

Cut the cheese slices and place them on top of the stuffed mushrooms.

Microwave the mushrooms until the cheese melts.