Preheat oven to 350 and grease a 9 X 13 casserole dish.

In a large skillet, melt 3 tablespoons of butter and add mushrooms, onion, minced garlic, salt, pepper, and nutmeg.

Saute on medium heat for 8-10 minutes until the onions are translucent and the mushrooms are soft.

Add chicken broth, cream cheese, and heavy whipping cream to skillet and simmer on medium-high until mixture reduces and thickens. Make sure to simmer with the lid off so that the moisture can evaporate and reduce. It took about 25 minutes or so for it to thicken. If you find it is not thick enough after 25 minutes, continue to simmer until it thickens. While it took 25 minutes on my stove, every stove cooks differently. If you have an immersion blender, you can blend up the diced mushrooms in the reduced cream of mushroom soup.

While the mushroom soup mixture is cooking, cover a cookie sheet with parchment paper. Sprinkle 2 cups shredded cheese, minced onion, parmesan cheese, and Italian seasoning on the parchment paper.

Bake until cheese melts and starts to brown so that it is crispy (approx 8-12 min). The cheese will bake together to form a large sheet. You can see the process pics above the recipe card in this post.

Remove from oven and cool, then break into small bites and lay the pieces on paper towels. The topping will crisp as it cools.

In a greased 13 X 9 baking dish, add 1 ½ cans of the green beans (drained), then add the mushroom soup mixture and sprinkle ¾ cup of shredded cheddar cheese on top.

Add the rest of the green beans, then top with the shredded mozzarella cheese.

Bake for 25 minutes, then remove the casserole dish from the oven.

Sprinkle the baked cheese on top and return to the oven for 5 minutes.

Allow to sit for 5 minutes before serving. Enjoy!