Beat together the butter and cream cheese in a medium-size bowl until smooth and creamy, about 3 minutes. Stir in by hand the flour and baking powder to make dough. Cover bowl and chill 2 to 3 hours.
Mix together the chopped nuts, apricot jam and the granulated sugar in a small bowl.
Heat oven to 350 degrees F.
Divide the dough into 4 equal parts. While working with a quarter at a time, refrigerate the remaining dough.
Roll out one quarter of the dough on a lightly floured surface very thinly, about 1/8 inch. Cut into 2-inch squares; you should have about 30 squares. Place half on baking sheet. Spoon 1 teaspoon of nut filling in the center of each square; top with another square of dough. Press the edges together with a floured fork to seal in the filling.
Bake in 350 degree oven 15 to 20 minutes or until lightly browned. Cool slightly on baking sheet on wire rack. Transfer the cookies to rack to cool. Repeat with remaining dough and filling, and bake. Dust with confectioners sugar, if desired. Makes 5 dozen cookies.