Instructions
Preheat your oven to 160°C (140°C fan or Gas Mark 3). Crush the digestive biscuits into fine crumbs. You can use a food processor for this. Alternatively, place biscuits in a strong plastic bag and crush them with a rolling pin. Melt the butter. Mix the melted butter with the biscuit crumbs. Press this mixture firmly into the base and up the sides of a 22cm loose-based tart tin. Bake the biscuit base in the preheated oven for 10 minutes. Remove the tin from the oven and let the base cool completely. Put the egg yolks into a large bowl. Whisk the egg yolks for 1 minute using electric beaters. Add the condensed milk to the bowl. Whisk for another 3 minutes until well combined. Zest and juice the limes. Add the lime zest and juice to the mixture. Whisk again for 3 minutes. Pour this filling into the cooled biscuit base. Place the pie back into the oven. Bake for 15 minutes. Remove the pie from the oven. Let it cool completely. Then, refrigerate the pie for at least 3 hours. For best results, chill it overnight. When you are ready to serve, carefully remove the pie from the tart tin. Place it onto a serving plate. To decorate, softly whip the double cream with the icing sugar. You can dollop or pipe this whipped cream onto the top of the pie. Finish by grating extra lime zest over the top.