Cut the potatoes into 1.5-inch chunks, trying to keep the chunks similar in size so they cook evenly. Place potatoes in a 3.5-quart saucepan. Cover with cold water, add one teaspoon of salt, then bring to a boil over medium-high heat.
Reduce heat to medium and gently simmer, adjusting the heat as needed, until the potatoes are fork tender, about 15 minutes. Drain in a colander, shake off excess water, and return to the saucepan.
Add the softened butter and mashed, roasted garlic cloves to the potatoes. With a potato masher or wooden spoon, smash the potatoes down to break them apart.
Heat the milk in a small bowl in the microwave until it is hot but not boiling. Pour over the potatoes. Add the sour cream (or Greek yogurt). Note: Start with a small amount of milk or cream and add more gradually until you reach the desired consistency. It’s easier to add more liquid than to thicken overly thin potatoes.
Mash and stir the potatoes until evenly combined. The potatoes should have a creamy texture, but not be perfectly smooth. There should still be small bits of potato remaining. Stir in any fresh herbs you may be using and adjust seasonings as needed.
Serve hot sprinkled with chopped chives and black pepper.
Notes
Use a potato masher or potato ricer instead of a food processor or blender, which can overwork the starches and make the potatoes gummy.
Yukon Gold Potatoes are creamy and buttery, which makes a richer mashed potato.
Russet potatoes are known for their high starch content and fluffy texture. You can’t go wrong with either type.
Mashed potatoes can be made a day ahead of time. Store them in the refrigerator and reheat gently on the stovetop or in the oven. Add a bit of milk or cream to maintain the creamy texture.
If your mashed potatoes are too runny, you can try cooking them gently on the stovetop to evaporate some of the excess liquid.
Store leftover potatoes in an airtight container in the refrigerator for up to 3-4 days. Reheat in a saucepan with a splash or two of milk to keep them from drying out.