Rinse unpeeled potatoes and soften in water. Steam briefly, then remove the peel. Press through the potato press and keep warm. In a bowl, heat the milk until lukewarm and let the butter melt in it. Add the mashed potatoes and heat repeatedly at a very low temperature, stirring continuously.
Remove the skin from the garlic and press it through a garlic press. Fry in olive oil until light and add to the mashed potatoes. Season with salt and freshly ground pepper, perhaps stirring repeatedly with a hand mixer. Rinse the basil, pluck off the leaves and chop finely, fold into the mashed potatoes with the oregano.
Immediately before serving, drizzle with truffle oil.