Step by step recipe:

1. 2 min.

   The lime filling

   
   
   Put 4 g gelatin to soak in cold water.
2. 3 min.
   Weigh 125 g egg, then whisk briefly until liquid.
   
   Note: once liquid, it is easier to adjust the weight more precisely if necessary. Use up any egg left over for glazing in another recipe.
   
   

   Set aside.

3. 4 min.
   Pour 125 g lime juice into a pan, add 125 g butter and 125 g caster sugar.
4. 7 min.
   Put the pan on medium heat and bring the mixture to the boil while whisking frequently.
5. 3 min.
   Add the eggs and bring back to the boil.
   
   Take off the heat.
6. 2 min.
   Finish by mixing in the gelatine (after draining well).
7. 3 min.
   It is not essential, but give the mixture a quick blast with a blender if possible to emulsify it slightly.
8. 3 min.
   If you wish to improve the appearence, add a few drops of green colouring to the filling.
   
   Cover and leave the filling to cool.
9. 5 min.

   The sweet pastry case

   
   
   Preheat the oven to 360°F (180°C).
   
   Roll out 250 g Sweet pastry and line your tart tin or mould (a 7 inch/18 cm square tin here).
   
   Prick all over the bottom with a fork or pique-vite (pastry pricker).
10. 15 min.
    Bake for 15 minutes.
    
    Leave to cool on a wire rack.
    
    :Note: To help keep the pastry crisp, you can use this technique.
11. 1 hour
    When both the filling and pastry case are cold, pour the filling into the case, level the surface by tapping the sides, then put to set in the fridge for at least 1 hour.
12. 5 min.

    The Italian meringue topping

    When the filling is set, pipe 200 g Italian Meringue over the top using a forcing bag.
13. 2 min.
    Colour the top of the meringue, either by putting the tart under a hot grill for a few seconds, or by using a torch.
    
    Decorate with a few shreds of lime zest.