Melt the butter and olive oil in a large skillet over medium heat.
Add the chopped onion and sauté for 2-3 minutes until translucent.
Add the minced garlic and cook for 1 minute until fragrant.
Add the spinach in batches and cook until wilted, about 5 minutes.
Season with salt and black pepper.
Add the heavy cream and cream cheese, and stir until the cream cheese is melted.
Stir in the grated Parmesan cheese.
Serve hot.
