In a large, heavy-bottomed skillet, heat the oil over medium heat. When hot, add the hot curry powder and stir it around for 30 seconds. Add the onions to the pan and saute until they are tender and a bit golden. When you’re there, add the carrots, potatoes, and minced garlic. Give it all a good stir, and then add about a half cup each of water and coconut milk. Stir in the turmeric, salt, and coriander.