Squeeze all of the water from the spinach. In a large pan, heat the oil over a medium heat. Add the shallots and cook, stirring, until softened, about 2 minutes. Add the flour and cook, stirring, for 30 seconds. Add the milk and broth and cook, scraping up any bits from the bottom of the pan. Bring to a simmer and cook for 2 minutes. Add the spinach and simmer until tender, about 5 minutes. Stir in the evaporated milk and nutmeg and season to taste with salt and pepper.