Preheat the oven to 190°C/Fan 170°C/Gas 5. First get the pastry base ready. Lightly grease a 23 x 33cm baking tin and line the base with parchment paper. Unroll the pastry and roll out into a rectangle that is roughly 3mm thick.
Trim the pastry into a neat 28 x 38cm rectangle and drape into the prepared baking tin. Freeze for about 10 minutes or until the pastry is solid. Line the pastry case with a crumpled piece of parchment paper and fill with baking beans or rice.
Transfer to the oven and bake for 20 minutes, then remove the beans/rice and parchment paper and bake for a further 10 minutes until lightly browned. Brush the inside with the beaten egg yolks, then bake for a further 2 minutes, or until the yolks are set.
Remove from the oven and set aside to cool.
To make the custard filling, place the caster sugar and cornflour into a large saucepan and whisk to combine. Add the remaining ingredients, except the butter, and whisk to combine.
Cook over a medium-high heat, whisking constantly, until the mixture comes to a simmer, then cook for a further 2 minutes until thick. Remove from the heat, stir through the butter until melted and smooth, then pour the custard into the baked tart case.
Press a sheet of clingfilm on to the surface of the custard to prevent a skin from forming. Leave at room temperature for an hour, then transfer to the refrigerator for at least 4 hours.
or the meringue topping, place the egg whites, sugar and cream of tartar into a large, heatproof bowl set over a pan of simmering water (ensuring the bottom of the bowl doesn’t touch the water underneath) and whisk until the sugar has dissolved.
You can tell when this mixture is ready by rubbing a little between your fingers. If it feels smooth it is ready, if you feel grains of sugar cook for longer.
Remove the bowl from the heat and, using an electric mixer, whisk until the meringue is stiff and glossy. Add the vanilla and bitters and whisk briefly to combine. Scrape the meringue on to the tart and spread evenly over the filling.
Using a blowtorch or under a preheated hot grill, burnish the meringue until toasted.
Kept in the refrigerator, without the meringue, this tart will keep for a couple of days, but my preference is to serve it as close to making as possible to keep the pastry at its crispest.