Method

• 1.
  Carefully remove the top of each egg using a serrated knife. Separate the eggs by passing them through your fingers and letting the eggwhite drip through your fingers into a bowl. Place yolks in a heatproof bowl. Wash out eggshells, then dry carefully with paper towel. Set aside.
• 2.
  Add butter, zest and juice and 100g sugar to the bowl with the yolks, then whisk until just combined. Set the bowl over a pan of simmering water (don't let the bowl touch the water). Stir gently with a wooden spoon for 6-8 minutes until the butter has melted and the lemon curd mixture has thickened. Cool.
• 3.
  Half-fill each egg shell with some of the cooled lemon curd. Place in ovenproof egg cups, then refrigerate while you make the meringue.
• 4.
  Preheat the oven to 220°C. Place the eggwhites in the bowl of an electric mixer with another 1/2 cup (110g) sugar and beat until soft peaks form. With the motor running, slowly add the remaining 1/2 cup (110g) sugar until mixture is stiff and glossy, then beat in the cornflour and vinegar.

• 5.
  Place meringue mixture in a piping bag fitted with a fluted nozzle, then pipe meringue into eggshells, about 3cm above the top. Place egg cups on a tray, then bake for 5 minutes or until the meringue is crisp and tinged golden. Serve immediately.