In a medium sauté pan, cook the bacon until crisp.

Add butter and onions, cooking until softened, about 3–5 minutes.

Add spinach and cook for another 2 minutes, or until wilted.

Remove the pan from the heat and add the nutmeg, flour, feta, plus

salt and pepper to taste. Let cool.

Stuff filling into mushroom caps and place on a cookie sheet.

Bake at 375°F for 15 minutes, or until the mushrooms are tender.

Serve hot.