Great grannie's shortbread

Method
Prep:15min  ›  Cook:50min  ›  Ready in:1hr5min 

1. Preheat oven to 150 C / Gas 2.
2. Cream together butter and sugar, with wooden spoon (not food processor), until creamy.
3. Add flours and salt, and work into the butter mixture with hands, until a smooth, soft dough forms. It may take several minutes, but do not overwork once dough is formed.
4. Press into a non-stick tin (I use 8"x11" tin), and flatten and spread dough until even throughout. Prick entire surface with fork.
5. Bake 50 to 55 minutes, or until very slightly browned on edges. While still hot, slice and sprinkle entire surface generously with extra sugar. Let cool slightly, then enjoy!