Preheat oven to 400°F. Tear out 4 large foil squares. Place a chicken breast in center of each; season with salt and pepper. In a small bowl, combine pineapple, jam, heavy cream and curry powder; spread over chicken. Top each with 1/2 Tbsp. butter.
Fold top of foil over chicken and crimp edges to seal. There should not be any gaps where liquid could seep out. Place packets on a rimmed baking sheet; bake for 20 minutes. Packets will puff with steam as they heat up if they have been sealed correctly.
Carefully open packets by cutting an X in center of each and peeling foil back; keep hands and face away from steam as it escapes from packets. Use a large spoon or tongs to transfer chicken to plates or a platter. Ladle sauce from inside packets onto chicken and serve hot, with rice and carrots, if desired.