Place the sweet potatoes in a medium saucepan and cover with cold water. Bring to a boil over medium-high heat, then reduce to a simmer and cook until the sweet potatoes are just tender, about 5 minutes. Drain and transfer to a large bowl.
Add the star fruit, jalapenos, lemon juice, chaat masala, cumin, chili powder and a pinch of salt and mix until combined. Drizzle with chutney and top with cilantro and pomegranate seeds. Serve warm or at room temperature.
Chaat is traditionally a snack, so this recipe makes a small portion; you might want to double it for a crowd.