For the potatoes: Cube the potatoes. Then put the potatoes in a large saucepan with salted cold water and place in the refrigerator overnight. The next day, add some more salt and then bring to a boil over high heat. Cook until tender, about 10 minutes. Drain well, place potato cubes in a food mill, and grind to remove skins. Alternatively, smash the potatoes with a large fork or potato masher.
04Heat 1 tablespoon of the butter in a large saucepan over medium heat until the butter stops foaming and turns a light brown. Add the garlic paste and cook quickly. Add the cream, season, to taste, with salt and pepper, and bring to a boil. Reduce the heat to low and fold in potatoes with a wooded spoon or large whisk. Add the remaining butter by tablespoons, stirring after each addition. Stir in the extra-virgin olive oil. Season with salt and pepper, to taste, and serve.