Scrub the potatoes well, removing any bad spots or eyes that you see. If any are larger than the others, cut in half to make sure they cook evenly.
Add potatoes to a large pot and cover with water and a pinch of salt. Place on the stove over high heat and bring to a boil. Reduce heat to a strong simmer and cook until fork tender, about 10-12 minutes.
Drain, then mash well in the same pot. Or, puree mixture in the pot with an immersion blender to make it even smoother.
Stir in butter and milk, and continue to stir until mixture is smooth.
Stir in garlic, parsley, salt, and pepper until combined. Season with additional salt and pepper to taste.