Preheat oven to 350°F, with a rack in the middle. Butter a cookie sheet.
Melt chocolate and let it cool down a little.
Cream butter; add egg yolks, sugar, and cooled chocolate.
Beat egg whites until stiff. Add to chocolate mixture along with flour, chopped walnuts, and spices, combining well. Pour onto prepared cookie sheet, spreading evenly.
Bake on middle rack for 25 minutes. Cool completely.
Heat the apricot jam with 2 tablespoons of water, and then press the mixture through a sieve to remove any lumps. Use a brush to coat the baked dough with the apricot jam.
Melt the chocolate icing and carefully pour over the apricot glaze. Place the walnut halves evenly over top and cool before cutting into 80 squares, each with a walnut half in the center.