Preheat oven to 400 degrees F. Lightly oil 4 10-ounce ramekins or coat with nonstick spray.
Melt butter in a large skillet over medium heat. Add mushrooms, garlic, thyme, and red paper flakes, if using. Cook, stirring occasionally, until tender, about 3-4 minutes; season with salt and pepper, to taste. Stir in spinach until wilted, about 2 minutes.
Divide mushroom mixture evenly into the ramekins. Top with eggs, heavy cream and parmesan; season with salt and pepper to taste.
Place into oven and bake until egg whites are just set, about 10-14 minutes.
Approx Nutrition per serving: 220kcal; 3.9g NET carbs; 11.1g protein