Bring a medium sized pot of salted water to boil. Blanche beans for about 5 minutes. Drain immediately and run under cold water. Set aside.
In a large skillet, cook pancetta until slightly crispy over medium heat. Transfer to paper towel lined plate.
Turn heat to medium low and melt butter. Add shallots and cook until fragrant, about 1-2 minutes. Add in garlic and cook for 30 seconds. Next stir in mushrooms and a healthy dose of salt. Stirring occasionally, let mushrooms cook down and release their juices, about 8-10 minutes.
Add beans and pancetta to mushroom mixture. Cook for 1-2 minutes more. then sprinkle with black pepper and parsley.