Sift flour, sugar and salt in bowl. Work butter into flour. Add egg yolks, then the sour cream and wine. Mix well. Turn out on floured board and knead until smooth. Divide dough into 2 or 3 pieces. Roll very thin. Cut into about 13 cm diamond shaped pieces. Fry in very hot deep fat about one or two minutes or until golden brown. When cool, dust with powdered sugar.