Pour the unsifted confectioners' sugar into a large bowl.
Cut the butter from the stick into small slivers, dropping them into the sugar.
Add the cream and vanilla or almond extract.
Work with your fingertips until the mixture clings together somewhat.
Turn the mixture onto a sheet of waxed paper.
Knead by pushing the mixture against the surface with the heel of your hand, lifting the edges of the waxed paper to add and incorporate any crumbs of dough.
Continue kneading in this manner until the mixture is well blended, smooth, and creamy.
Wrap in the waxed paper and chill just long enough so that the fondant can be handled easily without sticking.
Prunes: Slit the tops of the prunes and spread slightly.
Roll a small portion of the chilled fondant into a ball and press into the cavity.
Garnish with a sliver of candied cherry.
Cherries: Cut a cross in the top of each cherry; spread slightly to form petals.
Fill with a small ball of fondant and decorate the tops with a few silver dragees.
Dates: Cut the dates partway through and press a small portion of the fondant into the cavities.
Roll the filled dates in granulated sugar.
Walnuts or Pecans: Shape the fondant into small balls; place between two walnut or pecan halves; press together lightly.
Store in one layer in a tightly covered container in the refrigerator.
The sugarplums will keep well up to 2 weeks.