Palace shortbread

Palace shortbread

2      cup  cake flour
3/4  cup   +   1    tbsp    cornstarch
1/4  tsp    salt
1      cup   unsalted  butter     [ room temperature ]
1/3  cup  granulated sugar
1/4  cup  superfine sugar

1. in a medium bowl, together  flour, cornstarch, salt.
2. in big bowl, beat the butter until creamy on M-speed.beat in sugar until fluffy(2 min). on L-speed, add flour in 2 or 3 addition, form a dough. wrap and chill for 30 min.
3. preheat  oven to 350  F.  line with parchment paper or ungreased.
4. roll the dough to 3/4 inch thick, 5 X 8 inch.  bake 40 min.  while still warm, cut into pieces.