Bring a pot of salted water to a boil over high heat. Add the spinach and simmer for 2 minutes. Drain the spinach in a colander. Press down on the spinach with a clean kitchen towel to release all of the liquid. Remove to a cutting board and roughly chop.
Heat a large saute pan, over medium-high heat and add the butter and olive oil. When the butter has melted, add the shallots and garlic and saute until fragrant and tender. Stir in the red pepper flakes and spinach. Sprinkle with salt and pepper, to taste. Saute briefly, then add the heavy cream, nutmeg and Parmesan. Reduce the spinach mixture until it has thickened, about 2 minutes. Transfer to a serving bowl and serve.