Gently wash and dry mushrooms.
Slice into about 1/2" thick slices. Set aside.
Remove large stems and finely chop parsley. Set aside.
Melt butter in a large skillet over medium heat.
Add olive oil.
Add mushrooms to pan. season with salt and pepper.
Cook stirring occasionally until mushrooms are tender and developing nice color (abouqt 8 minutes).
Add garlic and half of the parsley.
Cook stirring continuously for 2-3 minutes.
Remove from heat.
Garnish with remaining parsley.