This potent Indian soup is known as kadhi, but there’s very little agreement on kadhi other than that it’s a sort of sour and spicy vegetable soup, made with plenty of buttermilk and fragrant with Indian spices and as hot as you like to make it with chiles.
A typical kadhi starts with cooking some bite-size vegetables, then sizzling whole spices in oil before adding water, buttermilk, and the chickpea flour, know as besan in Indian markets. The chickpea flour thickens the soup and helps prevent the buttermilk from breaking, though most kadhi recipes also remind you not to bring the soup to a boil, but merely to heat it through.
The last step is to make a tarka, or “seasoning,” by heating spices in clarified butter to drizzle over each serving. (If, like me, you don’t regularly keep clarified butter in your kitchen, it’s fine to use regular butter.) To make a bowl of kadhi more of a meal, put a cup of hot rice—a fragrant one like jasmine or basmati, ideally—in the bottom of each bowl before spooning in the soup.
Heat 1 tablespoon of the oil in a medium saucepan over medium heat. Add the onion and cook for 4 to 5 minutes, stirring often, until softened and just starting to brown. Add the potatoes, cauliflower, and green beans, along with 2 cups of water. Bring to a boil, then lower the heat, cover, and simmer gently until the vegetables are tender, about 10 minutes. Turn off the heat and leave the covered pot on the back of the stove.
Heat the remaining 1 tablespoon of oil in a large, heavy saucepan over medium heat. Add all the spices (peppercorns through ginger). Heat for 1 minute, stirring, until the ginger smells fragrant.
Add 1/2 cup of water and bring to a boil, then lower the heat and simmer for 5 minutes. Meanwhile, in a separate bowl whisk the chickpea flour into the buttermilk until smooth.
Pour the buttermilk mixture over the spices and heat through over low heat, stirring constantly. Cook for 5 minutes, continually stirring and being careful not to let the mixture boil. Add the cooked vegetables and their liquid to the saucepan. Season with salt to taste. Continue to cook over very low heat for another minute or two, just to heat through.
Pour the soup into bowls. In a small skillet or saucepan, heat the butter and add the chile powder. Roast the spice in the butter for 1 minute, then drizzle a little of the spicy butter over each bowl of soup. Serve at once.
From The Animal Farm Buttermilk Cookbook: Recipes and Reflections from a Small Vermont Dairy by Diane St. Clair/Andrews McMeel Publishing, LLC