Melt the butter in a large skillet / oven proof frying pan set over a medium heat. Add the garlic and cook, stirring until fragrant - about 1 minute. Add the chopped artichokes and stir until well coated in butter. Add the spinach, salt, pepper and nutmeg and continue to cook, stirring occasionally, until the spinach has wilted and most of the liquid is cooked off. Stir in the cream cheese and double cream and stir until everything has melted together. Add 100 grams parmesan and stir until melted and creamy. Taste and season with salt and pepper if needed. To finish, sprinkle over the mozzarella and 40 grams parmesan and place into the preheated oven for 10 minutes to brown the top - alternatively you could place under the grill for 3 - 4 minutes.