First, place the pancetta in a medium pan (medium heat) with teaspoon olive oil. Cook until crispy and then take out of pan.
Next, add butter, onions, mushrooms, salt, pepper, red pepper flakes to the pan with the pancetta oil. Stir and cook for 5 minutes. Then add garlic and green beans and cook 2 extra minutes.
Now, pour the veggie mixture in a casserole dish and mix in the can of cream of mushroom and sour cream.
Next, sprinkle the top with gruyere cheese and bake on middle rack at 375 for 25 minutes.
Finally, sprinkle fried onions on top and bake 5 more minutes. Enjoy!