Method

1. 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.

2. 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.

3. 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.

4. 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.