Pulse the garlic and ginger in a food processor until chopped. Add the fennel or celery, carrot, parsnip, and shallot and pulse until coarsely chopped.
Melt 2 Tbs. of the butter in a 4-qt. saucepan over medium-high heat. Add the chopped vegetables and cook, stirring, until softened, about 3 minutes. Add the curry powder and cook, stirring, until the curry powder is fragrant, about 30 seconds. Add the lentils, broth, salt, and pepper. Bring the soup to a boil over high heat, reduce the heat to maintain a brisk simmer, cover, and cook until the lentils are tender, 25 to 30 minutes.
Transfer 1-1/2 cups of the soup to a blender or a food processor and purée until smooth. Stir the purée back into the soup along with the remaining 1 Tbs. butter. Season to taste with salt and pepper, and adjust the consistency with water, if you like.
Garnish with a dollop of plain whole-milk yogurt and chopped fresh mint or cilantro, or both.
nutrition information (per serving):
based on four servings, Calories
11, Fat Calories
100, Saturated Fat
19, Monounsaturated Fat
43, Polyunsaturated Fat
Photo: Scott Phillips