In a pot add the potatoes, Fresh milk epilegmeno full fat 35%, the white part of the spring onion, the garlic, OLYMPOS cow butter and place over high heat.
Add salt and once it comes to a boil, lower the heat to medium, so that the food is simmering.
Occasionally stir softly by shaking the pot, trying not to break the potatoes.
Once potatoes get soft and the sauce thickens, remove the pot from heat, stir, taste and season to taste, if needed.
In a baking dish, spread half of the potato mixture, add the green part of the spring onion, sprinkle OLYMPOS gruyere cheese all over the top and repeat the process with one more layer.
Bake in preheat oven at 180οC for approximately 35 minutes, until a golden and crunchy crust is formed.
Remove the baking dish from the oven, set it aside to cool a little, serve and add some freshly-ground pepper on top.