Ingredients 

Pastry 
175g plain flour 
40g icing sugar 
2 heaped tsp ground ginger 
Salt 
100g butter, cut into chunks 
1 egg yolk 
1 tbsp cold water 

Or Biscuit Base 
200g ginger nut biscuits or speculoos cookies
50g melted butter 

Lime filling 
4 limes, grated zest and juice 
1 x 397g tin of condensed milk 
300ml double cream 

Italian Meringue  
225g sugar 
6 tbsp water  
4 egg whites 

Or ready made small meringues 

Equipment
Tin: deep 24cm tart dish

Method
Take a large bowl and put the flour, sugar, ginger and salt and mix.  Add the butter and rub through into the flour.  When the mixture resembles fine breadcrumbs add the egg yolk and 1 tbsp of cold water.  You now need to gently bring together into a dough.  All of the mixture should be sticking to the ball of dough - if it is not, slowly add more water ½ tsp at a time.  Wrap in clingfilm and put into the fridge for 20 minutes.  

After 20 minutes roll out the pastry on a lightly floured surface and carefully line the dish with the pastry, taking care not to trim the pastry yet.  Carefully prick the pastry all over with a fork.  Put greaseproof or baking paper over the pastry and put back into the fridge for another 10 minutes.  Preheat the oven to 190c. 

Trim the top of the pastry and put baking beans or rice over the baking paper and put into the oven for 15 minutes.  Remove the baking beans and put back into the oven for another 10-12 minutes until starting to go golden.  Cool in the tin. 

If you are making a biscuit base then finely crush the biscuits and add the melted butter.  Put into the tart tin and push into the base and up the sides.  This should be fairly thin. 

Make the filling by putting all the ingredients into a bowl or stand mixer and mixing until thick creamy and combined. 

Put the sugar for the meringue in a saucepan with the water and heat over a medium heat.  Without stirring, bring to the boil.  You need to cook until a sugar thermometer reaches 118c.  Expect this to take 5-10 minutes. 

Meanwhile top the base with the lime filling.   In another bowl, mix the egg whites with an electric hand whisk until they reach stiff peaks.  When the sugar is hot enough then very carefully and slowly pour the sugar syrup over the egg whites until the mixture is shiny and thoroughly combined.  You can now either use a piping bag to pipe around the edge of the tart or use a spoon.  Using a blow torch brown the meringue.   

If you are using shop bought meringues put on the top of the tart in whatever design suits you.