Heat oven to 160 degrees centigrade.
Line the dish with oven paper.
Leave the butter out to warm to room temperature.
Sieve the flours together.
Put the butter in a bowl and beat with a whisk until it becomes creamy.
Add the sugar and salt and mix.
Add the flours and stir in a cutting motion with a spatula.
When the dough becomes crumbly, gather it together in a ball.
Put the dough into the prepared dish and smooth out with a spoon.
Before cooking, use a knife to score the shortbread for easier cutting later.
Cook for 50 to 60 minutes in a 160 degree oven.
While still hot, cut the shortbread into fingers and cool on a wire rack.
Enjoy!