Make the ice cream first. Heat the milk
and cream in a pan to just below boiling
point. Stir together yolks and sugar, then
gradually whisk in the hot milk mixture.
Return to pan, heating gently and stirring
until thickened. Stir in the zest and juice,
and cool. Churn, then freeze until solid.
Can be made up to a month ahead.
To make the pastry, whizz flour and
butter in a food processor, then pulse in
icing sugar. Pulse in zest with enough
yolk mixture to bring the pastry together.
Roll out and line 8 deep, individual tart
tins. Chill for 30 mins.
Heat oven to 190C/170C fan/gas 5. Fill
tarts with baking parchment and baking
beans, and bake blind for 15 mins.
Remove beans and paper and bake for
10 mins more. Remove from oven. When
cool enough to handle, remove from tins
and sit on a baking sheet. Turn oven
down to 160C/140C fan/gas 3.
For the filling, melt chocolate in a bowl
over a pan of barely simmering water.
Beat the 2 whole eggs, extra white and
sugar until thick and pale – about 5 mins.
Fold in the chocolate, melted butter and
flour, then divide between the tarts.
Let the mixture settle for a few mins,
then bake for 25 mins. Leave to cool for
10 mins while scooping ice cream into
balls. Dust the tarts with a little cocoa,
top each with a scoop of ice cream.