Melt chocolate in top of a double boiler or metal bowl set over a saucepan of barely simmering water, stirring occasionally until smooth.
While chocolate is melting, line bottom and sides of an 8-inch square baking pan with foil, leaving a 2-inch overhang, then lightly oil foil.
Remove chocolate from heat and stir in fruit and nuts, then spread evenly in baking pan. Freeze until firm, about 20 minutes. Lift candy in foil from pan using overhang and transfer to a cutting board. Peel off foil and cut candy with a long heavy knife into 36 pieces.
• If you have more time, chill the candy in the refrigerator (instead of in the freezer) until firm, about 1 hour. • Candy keeps, wrapped well in foil and chilled, 2 weeks.