Cream the butter and sugar

• Place the butter in a bowl and sift in the icing sugar.
• Mix well until fully combined and smooth.

Add the egg white and vanilla

• Add the egg white and vanilla extract to the butter mixture.
• Mix until evenly incorporated.

Form the dough

• Sift in the flour, cornflour and salt.
• Add the lemon zest if using.
• Mix until a smooth dough forms.

Prepare the piping bag

• Double line the piping bag to prevent tearing.
• Fit it with the star-shaped nozzle and transfer the dough into the bag.

Pipe the rosettes

• Pipe small rosettes onto a baking tray lined with baking paper.
• Bake one test cookie first to check the dough holds its shape; if it spreads too much, mix in a little extra flour. If the dough is too stiff to pipe, add a teaspoon of cream.

Chill the piped cookies

• Place the piped cookies in the fridge to firm up.

Bake

• Preheat the oven to 170 °C.
• Bake the chilled cookies until they just start turning golden; bake a little longer for extra crunch.

Finish and serve

• Let the cookies cool on the tray.
• Enjoy as they are, or finish with sugar, a dip in chocolate or your favourite glaze.