Chicken Curry with Cashews

    1/2 stick (1/4 cup) unsalted butter
    2 medium onions, finely chopped (2 cups)
    2 large garlic cloves, finely chopped
    1 tablespoon finely chopped peeled fresh ginger
    3 tablespoons curry powder
    2 teaspoons salt
    1 teaspoon ground cumin
    1/2 teaspoon cayenne
    1 (3 1/2- to 4-lb) chicken, cut into 10 serving pieces
    1 (14.5-oz) can diced tomatoes
    1/4 cup chopped fresh cilantro
    3/4 cup cashews (1/4 lb)
    3/4 cup plain whole-milk yogurt

Heat butter in a 5- to 6-quart wide heavy pot over moderately low
heat until foam subsides, then cook onions, garlic, and ginger,
stirring, until softened, about 5 minutes. Add curry powder, salt,
cumin, and cayenne and cook, stirring, 2 minutes. Add chicken and
cook, stirring to coat, 3 minutes. Add tomatoes, including juice,
and cilantro and bring to a simmer, then cover and simmer gently,
stirring occasionally, until chicken is cooked through, about 40
minutes.

Just before serving, pulse cashews in a food processor or electric
coffee/spice grinder until very finely ground, then add to curry
along with yogurt and simmer gently, uncovered, stirring, until
sauce is thickened, about 5 minutes.