Heat a medium saucepan over medium-high. Add 1/2 cup unsweetened coconut and 1/4 cup chopped roasted cashews. Cook, stirring, until coconut is golden brown, about 2 min. Transfer to a large bowl. Return pan to heat, then add 1 tbsp butter, 1 tsp sugar, 1/8 tsp salt and 1 cup basmati rice. Stir until rice is glossy, 1 min. Add 1 cup light coconut milk and 3/4 cup water. Bring to a boil, then reduce heat to low. Simmer, covered, until tender, about 20 min. Stir into coconut and cashews.