Prep the mushrooms: Heat the oven to 400°F (200°C). Line a baking sheet with parchment. Gently twist out the mushroom stems and finely chop them. Wipe the caps clean with a damp towel; don’t rinse, or they’ll get soggy.

Pre-bake the caps: Toss mushroom caps with 1 tablespoon olive oil, a pinch of salt, and pepper. Arrange hollow-side up and bake for 8–10 minutes to release moisture. Tip out any pooled liquid and set aside. This step keeps them from getting watery later.

Cook the filling base: Warm the remaining 1 tablespoon olive oil and the butter in a skillet over medium heat. Add chopped mushroom stems and scallions. Cook 3–4 minutes until softened and lightly golden.

Add aromatics and greens: Stir in garlic, oregano, and red pepper flakes. Cook 30 seconds until fragrant. Add spinach and a pinch of salt. Cook until wilted and most moisture evaporates, about 2–3 minutes. Remove from heat and let cool slightly.

Mix the filling: In a bowl, combine the spinach mixture, feta, cream cheese or ricotta, lemon zest, 1 teaspoon lemon juice, and 1/3 cup breadcrumbs. Season with salt and pepper to taste. The mixture should be thick and spoonable, not runny. Add a touch more breadcrumbs if needed.

Fill and top: Spoon the filling into each mushroom cap, mounding slightly. Mix the remaining breadcrumbs with Parmesan and a drizzle of olive oil. Sprinkle over the tops for a crisp finish.

Bake: Return to the oven and bake 12–15 minutes, until the tops are golden and the filling is hot and set. If you want extra color, broil for 1 minute at the end, watching closely.

Finish and serve: Let cool for 3–4 minutes. Taste and add another small squeeze of lemon if you like brightness. Garnish with chopped parsley or dill and serve warm.