Preheat the oven to 160°C/140°C/Gas 3. For the pastry, blitz the flour, butter and almonds together in a food processor before adding the icing sugar, then the egg yolk. Continue to blitz until it forms a ball. Roll out the pastry to a thickness of about 2 cm. Wrap it in some clingfilm and place in the refrigerator for an hour to chill.
Once the pastry is chilled, divide into six and roll each of these out to a thickness of about 3 mm (I dust the pastry with a little icing sugar to stop it sticking). Place the pastry into the small tartlet pans or rings, covering the base and sides. Place the tartlet bases in the refrigerator for a further 30 minutes to relax the gluten in the flour. Prick the tartlet bases with a fork to stop them rising and bake in the oven for 10 minutes to ‘set’ the pastry; it should be just cooked but still pale.
For the tartlet filling, whisk the eggs, egg yolk, sugar, cream, and juice and zest of the lemon and lime together, before carefully pouring into the tartlet bases. Bake the filled bases for 7–9 minutes. Check after 7 minutes to see whether the mix has just set, it should still wobble a little when shaken. To make the meringue, you will need a spotlessly clean mixing bowl(I wipe mine with a little vinegar, or lemon juice, to remove any oil which will stop the meringue from setting firm).
Whisk the egg whites and vanilla to soft peaks. Next, make a sugar syrup. In a heavy-bottomed saucepan, add enough water to just cover the base, then add the sugar and heat until the mixture is boiling and the temperature reaches 115°C. Now, while continuing to whisk the egg whites, pour the hot sugar syrup in a slow stream into the mixing bowl. Keep whisking until firm peaks are formed. Spoon or pipe the Italian meringue onto the tartlets and use a blowtorch to caramelize it. Serve as they are, or gently warmed for 10 minutes in a very low oven to make them extra special.