Melt butter in a pressure cooker over medium low heat.

Add onion and cook 5 minutes or until soft.

Stir often.

Add mushrooms and cook 2 minutes.

Add rice and cook another 2 minutes.

Stir constantly.

Stir in broth and mix well.

Lock the lid in place.

Cook on high heat to bring to high pressure.

Reduce heat just enough to maintain high pressure.

Cook 7 minutes.

Turn off heat.

Allow pressure to come down naturally, about 10 minutes.

Tip lid away from your face and remove.

Stir in Parmesan cheese.

Season with pepper.