This is an updated version of a mango-stuffed chicken breast I served on various ships twenty-five years ago - a timeless combination. If you need to work quickly, skip the marinade and rub the chicken with a combination of 1 teaspoon of salt and a ½ teaspoon each of ground cumin, ground coriander, and freshly ground black pepper. Pair the chicken with couscous or quinoa.
Insert a small, sharp knife into 1 side of each chicken breast keeping the opening you make no bigger than 1 ½ inches long as you move the knife in an arc to create a large pocket along the length of the chicken breast (go only two-thirds or three-quarters down its length so you don’t break through the surface at the thinner end). Place in a glass or enamel bowl or square, glass baking dish.
In a food processor, combine the cilantro, garlic, cumin salt, cayenne, and lemon juice. With the motor running, gradually add the olive oil through the feed tube until the mixture is blended. Add the yogurt and quickly pulse once or twice more. (Alternatively, create the whole marinade by hand)
Pour the yogurt mixture over the chicken and toss to coat, pushing some marinade into the “pockets” as well. Cover and chill for 1 to 6 hours, turning occasionally.
Heat a charcoal grill to medium hot (when you can hold your hand 5 inches above the rack for 3 to 4 seconds) or preheat a gas grill to high, covered, for 10 minutes and then reduce the heat to medium. Insert slices of mango into the pocket of each chicken breast and seal the openings closed with metal turkey pins or tooth picks.
Grill the chicken on a lightly oiled grill rack, turning occasionally, until just cooked through, 10 to 12 minutes total. (Alternatively, broil the chicken for 7 minutes on each side or brown the chicken skin-side first in a large pan in butter and olive oil and then bake at 400F for 15 to 20 minutes, or until cooked through.) Remove the pins and serve. Garnish with the cilantro sprigs.