POTATO SOUP WITH INDIAN SPICES

Steps:

• Put butter in a heavy-bottomed soup pot over medium-high heat. Add onions and a little salt and cook, stirring, until softened and just beginning to brown, about 8 minutes. Add carrots and celery and cook for 5 minutes more.
• Add turmeric, ginger, cayenne and asafetida, if using. Stir to coat and cook for another minute or so. Add potato chunks and 6 cups water, and bring to a boil. Reduce heat to maintain a brisk simmer. Add a healthy pinch of salt and cook until potatoes are soft when pierced with a skewer, about 15 minutes. Taste broth and adjust salt and heat as necessary: 1/4 teaspoon cayenne should suffice to make the soup fairly spicy, but add a touch more if you like.
• Use a potato masher to crush some of the potatoes, then continue to cook for another 5 minutes or so. This will help to thicken the soup slightly and give it more body. Turn off the heat.
• Make the tarka: Heat ghee in a small skillet over medium, but don't let it get too hot. Lower heat and add garlic and cumin seeds. Cook, stirring, until garlic is barely colored and cumin seeds have begun to brown, a minute or so. Add mustard seeds and green chile, if using. When mustard seeds begin to pop, after another minute, add the tarka to the soup and stir in.
• Ladle soup into low bowls, garnish with cilantro and serve. Pass lime wedges at the table.