Preheat the oven: Set it to 400°F (200°C).
Line a baking sheet with parchment for easy cleanup.
Prep the mushrooms: Wipe the caps with a damp paper towel. Twist out the stems and gently scoop out the gills with a spoon if needed to make room for filling. Pat the caps dry.
Season the caps: Place mushrooms hollow-side up on the baking sheet.
Brush with olive oil and sprinkle lightly with salt, pepper, and half the Italian seasoning.
Par-bake the caps: Bake for 7–8 minutes to release moisture. Drain off any liquid from the pan and gently blot inside each cap with a paper towel. This prevents sogginess.
Cook the protein: While the caps bake, heat a skillet over medium.
Add turkey or chicken sausage and cook, breaking it up, until browned and cooked through, 5–7 minutes. Season with garlic powder, remaining Italian seasoning, and red pepper flakes.
Mix the filling base: In a bowl, stir together cottage cheese (or Greek yogurt), 2 tablespoons mozzarella, and Parmesan. Fold in the cooked sausage.
Add a pinch of salt and pepper to taste.
Sauce the caps: Spoon about 1 to 2 teaspoons of pizza sauce into each mushroom cap. Swirl to coat the bottom.
Stuff generously: Add a heaping spoonful of the protein mixture to each cap. Press gently so it fills the cavity without overflowing too much.
Add toppings: Sprinkle the remaining mozzarella over the stuffed caps.
Add optional toppings like chopped turkey pepperoni, diced peppers, or olives.
Bake to finish: Return to the oven for 10–12 minutes, until the cheese is melted, bubbling, and lightly browned.
Broil for color (optional): Broil on high for 1–2 minutes for a golden top. Watch closely.
Garnish and serve: Let them rest for 3–5 minutes. Top with fresh basil or parsley.
Serve warm.