1. Preheat an oven to 160C fan-forced (180C conventional).

2. Line two standard baking trays with baking paper.

3. If using a stand mixer, place the butter, sugar, vanilla and zest into a bowl fitted with a paddle, and beat on a medium speed until the mixture is pale, smooth and creamy. Scrape the sides of the bowl down with a spatula or scraper. If you don't have a stand mixer, add the ingredients to a mixing bowl and beat well by hand with a stiff spatula.

4. Add the egg and beat again until combined.

5. Sift the flour and baking powder together and add, mix slowly until a soft dough forms.

6. Divide the dough into 16 even-sized pieces and roll into balls. Press each ball gently onto the baking tray, 8 per tray.

7. Bake the cookies for 12 minutes or until cooked and lightly golden. Leave to cool on a cake rack.

8. To make the glaze, sift the icing mixture into a bowl and gradually add the lemon juice a few drops at a time, mixing with a spoon, until you have a thick but smooth icing.

9. When the cookies are cool, spoon a little icing over each cookie and allow to set.

Get baking in your own home with pastry whiz Darren Purchese's July 4 online cookie class, complete with ingredient kit, available to click and collect from Burch & Purchese in Melbourne's South Yarra or have delivered by Providoor (Victoria only).