Add a light drizzle of oil to a large pan (or use oil spray) over medium heat then add the spinach (you may need to work in two batches). Use a wooden spoon to press down, then begin stirring until the spinach has wilted. Remove and place in a bowl to one side, then use a fork to press down on the spinach and squeeze out as much excess water as possible over the sink.
Melt the butter into the pan then add the shallots. Fry until soft and golden, then add the garlic and fry for another 30 seconds or so. Pour in the cream then stir in the parmesan, salt, pepper and nutmeg. Simmer and stir for a couple of minutes until everything thickens, then stir in the spinach. Check for seasoning and adjust if needed. The sauce might be a little thick at the start, but the spinach should thin it back out again.
