Prepare the pastry: Quickly blend cold butter cubes and flour into small crumbs.

In a separate bowl, combine egg yolks with 2 tablespoons of water.

Blend the egg yolk mixture into the flour crumbs until the pastry reaches the right consistency, adding a few more drops of water if needed.

Roll out the cold pastry on a floured surface.

Place the pastry into a pie tin and refrigerate for 30 minutes.

Prick the bottom of the pastry in the pie tin.

Preheat the oven to 200°C/180°C fan/gas 6.

Blind bake the pastry for 15 minutes.

Prepare the filling: Slowly heat guava paste, 2 tablespoons of water, sugar, and lime juice until just blended.

Remove the guava mixture from heat.

Add butter, beaten whole egg, and egg yolks to the pan.

Heat at medium, stirring vigorously for a few minutes until blended.

Set the filling aside in the refrigerator.

Prepare the meringue: Whisk egg whites until stiff peaks form.

Slowly add sugar, whisking as you add a bit at a time.

Whisk in the cornflour until you have thick, glossy peaks.

Pour the guava filling into the pastry case.

Top with the meringue.

Bake for 18-20 minutes until the meringue is crisp and slightly colored.

Let the pie sit for at least an hour before serving.