Set pot to saute and pour in olive oil until hot. Put thighs in pot and brown both sides. Then remove meat.
Add diced onion, garlic, parsley, salt and pepper. Saute together for about 2 minutes while scraping bits of chicken off bottom of pot to deglaze. Pour in 1/4 c. chicken broth once onions have softened and finish deglazing pot.
Turn pot off. Add thighs back into pot.
Pour rest of chicken broth in around chicken. Pour melted butter on chicken as well as lemon juice.
Close lid and steam valve and set to high pressure for 10 minutes (for medium thighs with bone in).
Do a quick release and remove thighs, set aside to keep warm.
Set pot to saute again. In a small bowl whisk together cornstarch and a bit of water until smooth. When liquid in pot bubbles, add this and stir. Allow to thicken for a few minutes and turn pot off.
Serve thighs with sauce poured on top. Season with more salt and pepper to taste.