Place the potatoes in a pan, cover with cold water and season with salt.
Bring to the boil on a medium heat, bring the heat down a little and boil the potatoes for about 15 minutes (if medium size, allow more time depending on the size).
Drain the potatoes and leave to cool down.
Once they are easy to handle, peel the skin off and slice the potatoes evenly (not too thinly).
Preheat the oven to 180 C.
Brush a baking tray (i like to use a round baking tin 26-28 cm in diameter) with some olive oil
and neatly arrange inside the sliced potatoes, which should overlap a little.
Cut into small pieces (or coarsely grate the Fontina cheese) and distribute all over the potatoes.
Cut into small cubes the butter and dab it all over the top.
Mix some salt with the milk and slowly pour it all over.
Season the dish with some pepper and bake in the preheated oven for 20 minutes finishing it off with 5 minutes under the grill, or until the top turns beautifully golden in colour.