Clean the spinach, wash it thoroughly and put it in a saucepan as it is, dripping wet, over a low heat (without adding any more water). Stir well once or twice and it will only take a few minutes to cook. Strain the spinach, then squeeze it well with your hands, shape it into balls and chop coarsely with a knife. Heat the oil in a pan with the clove of garlic; when the garlic begins to brown, remove it and tip in the spinach. Cook over a very low heat, stirring with a wooden spoon; add the milk and grated pecorino, continue stirring for 3-4 minutes and season with salt and pepper. Now put the spinach in a tall, narrow container and purée it with an immersion blender. Pour it back into the pan and, stirring, let the purée thicken over a low heat. Before serving, garnish with a few flakes of aged pecorino and a “drizzle” of olive oil (which adds a touch of flavour and goes well with everything… or almost!).