Preheat oven to 350 F.
In a large skillet over medium heat, add in chopped bacon and cook until crispy. Once golden, transfer to a plate lined with paper towel and set aside. Reserve half of the bacon grease in the pan.
Add in the diced mushrooms, garlic, and butter, and sauté until golden brown. Next add in the flour and stir to combine and allow to cook for 30 seconds or so, while continuously stirring to prevent burning.
Add in the green beans and add salt and pepper to taste, mix thoroughly. Cook for 6-8 minutes.
Add in the cream and half of the cooked bacon. Mix thoroughly and transfer to a baking dish.
Top with shredded mozzarella cheese, the rest of the cooked bacon, half of the fried onions, oregano, and top with a drizzle of olive oil.
Allow to bake for 25-30 minutes or until the top is golden brown and bubbling.
Once out of the oven, top with remaining fried onions.
Let it cool for a few minutes before serving and enjoy!