Heat the oven: Preheat to 400°F (205°C). Lightly grease a rimmed baking sheet or line it with parchment.

Prep the mushrooms: Wipe the caps clean with a damp paper towel. Twist out the stems, finely chop them, and set aside. Lightly brush the caps with 1 tablespoon of olive oil, then place them hollow-side up on the baking sheet. Sprinkle with a pinch of salt.

Sauté the aromatics: Heat the remaining 1 tablespoon of olive oil in a large skillet over medium heat. Add the onion and chopped mushroom stems. Cook, stirring, until softened and most moisture is gone, about 5–6 minutes. Add the garlic and cook 30 seconds more, until fragrant.

Brown the turkey: Add the ground turkey to the skillet. Season with 1 teaspoon salt, 1/2 teaspoon black pepper, the Italian seasoning, and red pepper flakes if using. Cook, breaking it up, until no longer pink and lightly browned, about 6–8 minutes. Remove from heat and let it cool for 3–4 minutes.

Make the filling: In a large bowl, combine the softened cream cheese, Parmesan, bread crumbs, parsley, and lemon zest if using. Add the slightly cooled turkey mixture. Stir until everything is evenly blended and creamy. Taste and adjust seasoning.

Stuff the caps: Spoon the filling into each mushroom cap, mounding it slightly. Press gently so it adheres. Sprinkle a little extra Parmesan on top for a golden finish.

Bake: Roast for 16–20 minutes, until the mushrooms are tender and the tops are lightly browned. If you want deeper color, broil for 1–2 minutes at the end, watching closely.

Garnish and serve: Let them rest 3–5 minutes to set. Shower with fresh parsley and a few cracks of black pepper. Serve warm.