Crush the 250g packet of plain sweet cookies in a food processor or by placing them in a bag and bashing with a rolling pin.
Mix the crushed cookies with 125g of melted butter until it resembles wet sand.
Press the cookie mixture into a 22cm springform cake tin, going up the sides slightly.
Chill the base in the fridge for 30 minutes.
In a saucepan, mix together 1 cup of castor sugar and ½ cup of corn flour/starch.
Gradually add in ½ cup of lemon juice and 1 cup of water, stirring to combine.
Cook the mixture over medium heat, stirring constantly, for 3-4 minutes until it boils and thickens.
Remove from heat and stir in 50g of chopped butter and 3 egg yolks until smooth.
Pour the lemon filling over the chilled cookie base and smooth the surface.
Chill the pie in the fridge for 1 hour to set.
In a mixing bowl, beat 3 egg whites with an electric mixer until soft peaks form.
Gradually add in ½ cup of castor sugar, beating until the meringue is glossy and stiff.
Spoon the meringue over the lemon filling, creating peaks and swirls.
Bake the pie in a preheated 220°C oven for 5-10 minutes until the meringue is golden.
Chill the pie in the fridge for at least 30 minutes before serving.
