In a wide skillet over medium heat, melt the butter. Add the onion and saute until translucent.
Add garlic and saute for 3-4 minutes; add spinach, and use tongs to cook until wilted.
Pour the cream over and sprinkle the cheese in. Mix until combined, simmer until thickened and creamy.
If desired, use an immersion blender to smooth out the mixture a bit more.