Preheat the oven to 425.

Carefully remove the stems from the mushrooms, place the stems onto a cutting board, then finely dice the mushroom stems.

Heat a sauté pan over medium-high, add the olive oil, onions and mushroom stems, and sauté for 3-5 minutes until softened.

Add the Boursin, allow it to melt and mix it into the sautéed veggies, then turn off the heat.

Add the spinach, feta and Parmesan to the pan and mix to combine to form a stuffing mixture.

Add the mushrooms to a baking dish, drizzle the tops with olive oil and season with some salt.

Add about 1 tablespoon of the mixture to each mushroom and press down with a spoon to form a top.

Add Parmesan cheese to the tops, then drizzle the tops with some olive oil.

Place them in the oven for 20 minutes.