Clean mushroom by wiping it with damp paper towels gently.
Remove stem and inner part of the mushroom and chop it about the same size as minced onion, garlic and green chilies.
Brush mushroom caps with olive oil the season lightly with salt and ground black pepper; set aside.
Preheat grill over medium high fire/heat.
Put the chopped mushroom stem, garlic, onion and green chilies in a large bowl; add ricotta cheese, pesto and parmesan cheese.
Season with salt and ground black pepper. Mix well until combined.
Spoon pesto filling into the hollow side of mushroom caps.
Top with graded mozarella cheese.
Arrange on the hot grill; cover loosely with aluminum foil.
Cook for about 15-20 minutes.
Serve immediately. Enjoy:)