Combine butter and cream cheese in a large mixing bowl, beating well.
Combine flour, sugar, and salt in a small mixing bowl. Add to creamed mixture, stirring well. Stir in whipping cream and vanilla; mix well. Cover and refrigerate overnight.
Roll to 1/8-inch thickness on a lightly floured surface; cut with a 2-inch round cutter. Place 1/2 teaspoon jelly in center of cookie; sprinkle with pecans. Fold opposite edges over filling and pinch together, forming a cornucopia. Brush open end of cornucopia with egg whites; dip in pistachio nuts. Repeat procedure with remaining cookies, egg whites, and nuts.
Place 2 inches apart on lightly greased cookie sheets; bake at 325° for 15 minutes. Remove from cookie sheets, and cool on wire racks.