Preheat oven to 375°F (190°C). Line a baking sheet with parchment paper.
- Clean the mushrooms by removing stems and gently scraping out the gills. Brush both sides with olive oil and season with salt and pepper.
- Place mushrooms gill-side up on the baking sheet and bake for 10 minutes to soften and release moisture.
- While mushrooms bake, heat a small skillet over medium heat with a little olive oil. Sauté garlic, spinach, and cherry tomatoes until wilted, about 2–3 minutes. Remove from heat.
- Remove mushrooms from oven and blot out any excess moisture with a paper towel. Spoon the spinach-tomato mixture into each mushroom.
- Sprinkle cheese over the filling, then carefully crack an egg into each mushroom cap.
- Return to oven and bake for 12–15 minutes, or until egg whites are set and yolks are cooked to desired doneness.
- Garnish with fresh herbs, season with extra salt and pepper, and serve warm.