2 1/2 cups Sugar
2 1/2 cups Orange Juice preferrably fresh
Cut both the ends off the oranges so they will sit flat, then cut them in half.
Cut around the inside of the rind to remove all the pulp (discard or eat); then use a paring knife to carefully remove as much of the white pith as possible.
Combine 2 cups of the sugar with 4 cups water in a saucepan and bring to a boil.
Add the orange shells, lower the heat, and simmer for 1 1/2 hours. Cool.
Meanwhile, combine the remaining 1/2 cup sugar with 1/2 cup water in a small saucepan.
Bring to a boil, stirring, then cool slightly and stir into the orange juice.
Freeze in an ice cream maker according to the manufacturer's directions.
Spread the sorbet into the orange shells and freeze on a tray for 30 minutes before serving.
Decorate with the pine nuts, as if they are orange pits, and serve.
The same procedure will work equally well with grapefruit, lemon, and lime, although you'll need to adjust the amount of sugar.