Preheat the oven to 180C / 350F / 160C fan forced. Line two baking trays with baking paper.
Optional: Scatter the pecans on a baking tray and bake for 7-8 minutes to toast them, the let them cool.
In a medium bowl (or the bowl of a standmixer with paddle attachment), beat the butter and sugar until pale and creamy.
Add the flour and cornflour and beat until it looks like wet sand.
Add the pecans and beat to incorporate. Pull the dough together with your hands.
Roll the dough out between two sheets of baking paper to about 8mm (⅓ inch), then use a 5cm (2 inch) cookie cutter to cut out circles.
Space about 2 inches apart on the baking trays then chill for 10 minutes.
Bake for around 14 minutes or until the edges start turning golden.
Let the cookies cool for a few minutes before transferring to a wire rack to cool completely.
Optional: dust all over with icing (powdered) sugar.
I use a standard Australian 20ml tablespoon (equal to 4 teaspoons worldwide)
All ovens vary. Check 2-3 minutes before the recipe suggests and an oven thermometer is very handy
Always weigh ingredients like flour or sugar as different forms of measuring give different results. Kitchen scales are cheap and last forever, but if you can't weigh use the spoon and level method - don't tap it down.
You can swap the cornflour for plain flour or swap both flours for cake flour.