Divide the butter: one half for spinach cooking, other for the cream sauce.
Melt 2 tbsp of butter in a deep frying pan over medium heat. Crash garlic with a flat side of knife and add it to the melted butter, toast for 20 seconds. Add spinach, stir, cover and cook for 5 minutes. Remove the lid and cook until all liquid has evaporated (about 5 more minutes). Spice with salt, pepper, nutmeg and 1 tbsp of butter. Remove from heat, cool slightly, remove the garlic. Add grated cheese and stir.