Directions

1. Heat the oven to 160C/fan 140C/gas 3.
2. Whizz 300g Hob Nobs to crumbs in afood processor(or put in a strong plastic bag and bash with a rolling pin).
3. Mix with 150g melted butter and press into the base and up the sides of a 22cm loose-based tart tin. Bake in the oven for 10 minutes. Remove and cool.
4. Put 3 medium egg yolks in a large bowl and whisk for a minute with electric beaters.
5. Add a can of condensed milk and whisk for 3 minutes, then add the finely grated zest and juice of 4 limes and whisk again for 3 minutes.
6. Pour the filling into the cooled base then put back in the oven for 15 minutes. Cool then chill for at least 3 hours or overnight if you like. When you are ready to serve, carefully remove the pie from the tin and put on a serving plate.
7. To decorate, softly whip together 300ml double cream and 1 tbsp icing sugar.
8. Dollop or pipe the cream onto the top of the pie and finish with extra lime zest.