Prepare the Pastry Cases:

• Generously grease a mini cupcake tray with butter.
• Unroll the shortcrust pastry and use a 2-inch round cutter (or the rim of a glass) to stamp out circles. If you want to make flower-shaped tartlets, use a flower-shaped cookie cutter instead.
• Press the pastry circles into the mini cupcake tray. If making flower tartlets, only fill every other one and fold the petals outwards onto the surface of the tray.
• Prick the bottom of each pastry case with a fork to prevent them from puffing up during baking.
• Place the prepared tray in the fridge for 1 hour to chill the pastry.

Bake the Pastry Cases:

• Preheat the oven to 180°C fan / 200°C conventional.
• Bake the pastry cases for 15 minutes, or until they are light golden brown and cooked through.
• Remove the tray from the oven and let the pastry cases cool in the tray for 10 minutes before carefully transferring them to a wire rack to cool completely.

Make the Lemon Curd:

• While the pastry cases are cooling, prepare the lemon curd.
• In a medium-sized saucepan, combine the lemon zest, lemon juice, caster sugar, and butter.
• Place the saucepan over medium-low heat and stir until the butter melts and the sugar dissolves. This should take about 5 minutes.
• In a separate bowl, whisk together three egg yolks and one whole egg.
• Pour the whisked eggs into the saucepan and whisk to combine with the lemon mixture.
• Turn the heat up to medium and whisk continuously until the lemon curd thickens and coats the back of a spoon. This can take 5-10 minutes.
• Once thickened, strain the lemon curd through a sieve into a bowl to remove the lemon zest.
• Leave the lemon curd to cool and thicken for about 10 minutes.

Assemble the Tartlets:

• Generously dust the cooled pastry cases with icing sugar.
• Fill each pastry case to the top with the lemon curd.
• Place the filled tartlets in the fridge to set for at least 30 minutes before serving.