Wash your potatoes (I always leave the skin on, but you can peel them if you like) and chop into small chunks. Place in a saucepan of boiling water and boil for around 15 minutes, or until just soft enough for you to stick a sharp knife in.
Whilst the potatoes are cooking, dice the onions and fry in a tiny bit of oil for around 10-15 minutes, or until they're just how you like them.
Throw the potatoes, onions, garlic powder, onion powder and rosemary into a large bowl. Scoop in 1/4 cup of yogurt and toss until everything is well coated. Taste and add salt, pepper and more yogurt to your liking.
Serve immediately or leave in the fridge to cool before serving.