Peel and dice the potatoes into 1.5 inch (3 cm) chunks. Place in a large pot and add enough water to fully cover the potatoes by about 1 inch (2 cm). Cover and bring to a boil.
Remove the lid and then reduce the heat to keep it at a low simmer (so that they don't boil over). Cook for 15-20 minutes until fork tender, checking every minute or so after the 15 minute mark (you should feel almost no resistance when you poke it with a fork).
Reserve 1 cup of the liquid and the drain the rest of the water off of the potatoes.
Using a hand masher, mash until creamy. Add in the yogurt and seasonings until just combined, adding reserved water if needed to reach desired consistency.
Serve warm.
Notes
LeftoversStore leftovers in an airtight container in the refrigerator for up to 4 days. Reheat in the microwave or on the stovetop with a splash of water (or milk) until heated through.