While the artichokes and pasta cook, in a saucepot over medium to medium-high heat, add the butter. When melted, whisk in the flour for 1 minute or so, then whisk in the milk and season with salt, pepper and a little nutmeg. Cook 5 to 6 minutes, or until thick enough to coat the back of a spoon, adjust the seasonings and stir in the Gruyere cheese. Combine the sauce with the spinach, pasta, and artichoke and stir until just combined. Transfer the mixture to a baking dish and cover with the remaining cheese. Cool and store for a make-ahead meal.
Bake on a baking sheet 45 minutes or until brown and bubbly on top.