Rinse and pat dry the mushrooms, removing any debris.

Heat a large, heavy bottomed skillet over medium heat. Add the butter to the skillet.

When the butter has melted add the onion and cook for 5 minutes, stirring often, to soften onions.

Add the sun-dried tomatoes and garlic and cook for 2-3 minutes.

Add the mushrooms to the skillet and cook, stirring often, about 5 minutes.

Add the heavy cream to the pan and let cook for 1-2 minutes to warm through.

Add the spinach and stir well. Continue cooking over low heat until spinach has wilted and sauce has thickened slightly, about 3 minutes.

Season with salt and pepper, to taste and serve hot.