Tapioca Pilaf

Bring water (10 cups) to a boil in a 3-to 4-quart pot. Add tapioca pearls and simmer, uncovered, stirring occasionally, 30 minutes. Remove from heat and let stand, covered, until pearls are translucent around edge, have a white center, and are al dente, about 45 minutes more.
While tapioca stands, cover taro with cold water in a small saucepan. Bring to a simmer, then simmer until almost tender, 12 to 15 minutes. Transfer taro to a cutting board. When cool enough to handle, cut into 1/4-inch dice.
Drain tapioca in a sieve and rinse well under cold water. Let stand in sieve submerged in a bowl of cold water until ready to use.
Heat butter in a 12-inch nonstick skillet over medium-high heat until hot, then sauté taro until just tender and golden, about 5 minutes. Add chile and garlic and sauté until softened, 30 seconds to 1 minute. Add mustard seeds, cumin seeds, and neem leaves (if using) and sauté until fragrant, about 30 seconds more.
Lift sieve with tapioca out of water and shake to drain well. Add to taro mixture in skillet along with peanuts and 1/2 teaspoon salt and sauté 2 minutes. Toss with cilantro and serve immediately.