Place potatoes in a pot and cover with water. Bring up to a boil, salt water and cook until tender, 12 to 15 minutes.
To a small skillet over medium heat add a little extra-virgin olive oil and bacon and brown, 7 to 8 minutes. Add onions and cook until soft, 5 minutes more.
Drain the potatoes and place back in the hot pot. Add bacon, onions and defrosted spinach to potatoes, mash to combine then add cream. Mash until smooth and season the mixture with salt, pepper and nutmeg.