Bacon and Spinach Stuffed Portobello Mushrooms

1 ½ tsps of extra-virgin olive oil (about half a turn of the pan)
4 portobello mushrooms, cleaned with gills and stems removed
3 to 4 slices of thick cut bacon, cut into ½ inch pieces
1 medium white onion, diced
4 cloves of garlic, minced
1/2 tsp red pepper flakes (optional)
6 cups of fresh baby spinach or 1 (10-ounce) box of frozen spinach, defrosted and squeezed dry
1/8 tsp nutmeg
½ cup of bread crumbs (about two generous handfuls)
½ - ¾ cup of crumbled feta, grated Parmigiano (or any other cheese on hand)
salt and pepper, to taste

Preheat the oven to 400 degrees.
Cover a baking sheet with aluminum foil and a light drizzle of oil. This will prevent anything from sticking to the baking sheet and makes for easy cleanup.
Heat a large skillet over medium high heat. Add the oil and portobello mushrooms (cap side down). Cook for about one minute, on that side only, until they are lightly browned.
Remove the mushrooms and place them on the prepared baking sheet.
If you are not using bacon, skip this step. In the same skillet as the mushrooms, add the bacon and cook it until golden brown and crispy. Remove the bacon with a slotted spoon onto a plate and set aside.
In the same skillet with the bacon drippings, add the onion, garlic and red pepper flakes and let them cook for 1-2 minutes, until the onions start to sweat and you can smell the garlic. Note: If you are not using bacon drippings, you may want to add another drizzle of oil to the pan.
Add the spinach to the pan and cover with a lid so the spinach wilts Add the nutmeg.
Remove the pan from the heat. Add the bread crumbs, cooked bacon and cheese. Season lightly with salt and pepper.
Divide the mixture between your mushrooms. If you’d like, top them with a little more of the cheese.
Bake them for about 20 minutes or until golden brown and crispy on top. Serve immediately.