- In a deep saute pan heat the olive oil and 1 1/2 Tablespoon butter over medium high heat. Sauté the onion until translucent about 2 minutes then add the garlic, hot pepper flakes and cook for another minute.
- Slowly add the spinach leaves until they begin to wilt. Add 1/4 cup of the broth, add salt and pepper to taste, cover the pan with lid, and cook over medium heat.
- Once the spinach wilts, about 5 minutes, uncover and continue to stir. Don't let all of the moisture evaporate. You may have to add a little bit of water.
- In the remaining 1/4 cup chicken broth whisk in the flour until it's dissolved.
- Slowly pour the broth over the spinach and mushrooms and continue to stir until thick. Add a dash of nutmeg.
- Stir in 2 Tablespoons of the Parmesan cheese.
- Pour the mixture into a buttered gratin pan or glass casserole.
- Preheat oven to 375 F.
- In a bowl mix the Panko crumbs and Parmesan cheese. Melt the remaining butter and add that to the topping and mix well.
- Sprinkle the topping evenly over the spinach gratin.
- Bake until heated through and slightly golden brown on top, about 30 minutes.