Add the butter and sugar to a food processor. Pulse until the mixture is well combined and homogenous.

First, add the whole egg to the creamed mixture with the food processor running, and pulse until combined. Then add the egg yolk and vanilla and pulse again.

Sift together the flour and salt and add this flour mixture to the egg and butter mixture all at once. Pulse until a dough forms, do not overmix.

Remove the dough from the bowl, cover it in a sheet of plastic wrap, and refrigerate for an hour.

Preheat the oven to 140°C (290°F) and brush 20 mini tart tins with melted butter.

Remove the chilled dough from the fridge and roll it out on a lightly floured surface to a thickness of ½ cm (¼ inch) using a rolling pin.

Cut discs of the rolled pastry slightly larger than the tart tins, place these pastry discs into the buttered tart tins, and use your fingertips to gently press the pastry into the base and sides of the tins.

Line each pastry tin with parchment paper and fill this with uncooked rice or pie weights. Blind bake the shells in a preheated oven for 15 minutes until a light golden brown. Set aside.

In a large mixing bowl add the condensed milk, egg yolks, fresh lemon juice, and lemon zest. Whisk to combine.

Spoon the lemon mixture into the pre-baked pastry shells, be sure to fill them almost to the top.

Bake the filled tarts in a preheated oven at 160°C (320°F) for 15 minutes or until the lemon filling is just set.

Remove the tarts from the oven and allow to cool in tins for 15 minutes before removing and cooling completely on a wire rack.

Add the egg whites and sugar to a heat-proof bowl set over simmering water. Whisk continuously until the sugar has melted.

Once melted, beat the mixture in a stand mixer until stiff peaks form. Pipe onto each tart and torch until golden.