Spicy Peanut Chicken Over Rice

1 tablespoon peanut oil
1 cup chopped onion
1 1/2 tablespoons minced garlic (about 4 cloves)
2 1/2 lbs skinless, boneless chicken breast halves, cut into 1-inch pieces
1/3 cup chunky peanut butter
1 1/2 teaspoon curry powder
1 teaspoon salt
1 teaspoon crushed red pepper
1/2 teaspoon freshly ground black pepper
1 (6 oz) can tomato paste
3 cups chopped plum tomato (about 6)
2 (14 oz) cans chicken broth
8 cups rice
3/4 cup Greek-style yogurt

Heat oil in a Dutch oven over medium heat. Add onion and garlic to pan; cook 5 minutes or until tender, stirring frequently. Add chicken to pan; cook 4 minutes, or until chicken is done, stirring frequently. Stir in peanut butter and next five ingredients (through tomato paste); cook one minute. Add tomato and broth to pan; bring to a boil. Reduce heat, and simmer 30 minutes or until slightly thickened, stirring occasionally. Serve chicken mixture over rice; top each serving with yogurt.