Preheat your oven to 375°F (190°C).

Clean the Portobello mushrooms with a damp cloth and remove the stems.

Chop the mushroom stems finely and set aside.

In a skillet, heat olive oil over medium heat, then add chopped garlic and mushroom stems, sautéing until fragrant.

Add the spinach to the skillet and cook until wilted, then remove from heat.

In a mixing bowl, combine cooked spinach mixture with ricotta cheese, Parmesan cheese, Italian seasoning, and a sprinkle of salt and pepper.

Stuff each mushroom cap generously with the cheese and spinach mixture, packing it in well.

Place the stuffed mushrooms on a baking sheet lined with parchment paper.

Bake in the preheated oven for 25–30 minutes, or until the mushrooms are tender and the filling is lightly golden.

Remove from the oven and allow to cool for a few minutes.

Serve warm, garnished with extra Parmesan or fresh herbs if desired.