Pumpkin Mousse

1 1/4 cups cold milk
1 cup canned solid-pack pumpkin
1 teaspoon grated orange rind (optional)
1/4 teaspoon each cinnamon, nutmeg and ginger
    or 3/4 teaspoon pumpkin pie spice
1 small box vanilla or butterscotch instant pudding mix
1 cup thawed Cool Whip