How to Make It
Heat 1½ tablespoons oil in a large, high-sided skillet with a lid over medium-high. Season chicken with curry powder and 1½ teaspoons salt. Cook half the chicken, flipping once, until browned, about 2 minutes per side. Transfer to a plate. Repeat with remaining 1½ tablespoons oil and chicken.
Chop cilantro stems to equal ¼ cup; set leaves aside. Return skillet to medium-high. Add cilantro stems and shallot; cook, stirring often, for 30 seconds. Stir in 1½ cups coconut milk, ¼ cup water, and remaining ½ teaspoon salt, scraping up any browned bits. Add rice and chicken; bring to a boil. Reduce heat to medium-low. Cover and cook until rice is tender and liquid is absorbed, about 12 minutes. Remove from heat and let steam, covered, for 5 minutes.
Meanwhile, stir peanut butter, lime juice, tamari, sugar, and remaining ¼ cup coconut milk in a bowl. Drizzle sauce over rice and chicken; top with cilantro leaves. Serve with cucumber.