Peel, rinse and cube up 3 pounds of Yukon Gold potatoes
Place the potatoes into a large pot of cold water, covering them by at least 1 inch
Place the pot over high heat and bring the water to a boil
Once the water is boiling, add a large pinch of salt and reduce the heat to medium
Boil the potatoes until they are easily pierced by a fork, but not mushy
Transfer the potatoes into a strainer and set them aside
Add 2/3 cup of whole milk, 1/3 cup of sour cream, 4 tablespoons of butter, 1 teaspoon of salt and 1/2 teaspoon of black pepper into the pot your potatoes were boiled in
Place the pot over medium heat
Once the butter has melted, transfer the pot onto a heat proof surface, such as a wooden cutting board
Transfer the drained potatoes back into the pot and mash with a potato masher or whip with an electric hand mixer until smooth and creamy
If the potatoes are too tight, add the remaining 1/3 cup of whole milk
Taste and add additional salt and pepper, if necessary
Garnish with finely chopped parsley and a few extra pats of butter