Gently place the potatoes into a large saucepan, filling it with enough cold water to ensure they are fully covered. Bring the pan to a rolling boil and allow them to cook until they become tender.
Drain the potatoes in a colander, leaving them to cool for around 5 minutes.
Return the cooled potatoes in back in their pot and, using either a potato masher or fork, mash them to your desired texture.
Incorporate butter, garlic, sour cream and milk into the mashed potatoes and mix everything together until all ingredients are thoroughly combined.
Taste for seasoning and add salt if needed in order to enhance the flavor of your dish.
Serve hot with a garnish of parsley or chives for a pop of freshness.