Peel and thinly cut the potatoes into round slices.
Heat the butter in a pot and add garlic, thyme, and spring onion. Sauté until fragrant.
Add the milk, season with salt and pepper, then add 250g mozzarella and slightly heat until it thickens into a sauce. You add cream then baby spinach & cool for 5 minutes.
In an oven-proof dish, add the sliced potatoes and sauce so the potatoes are covered.
Top with the remaining 100g of mozzarella. Place in a preheated oven and bake for 90 minutes at 180˚C. Cool and serve.
