1. Put the apples in a pan with 15ml/1tbsp of water and 75g/3oz caster sugar. Cook on a gentle heat until soft.
2. Pass through a fine sieve and return to a clean pan.
3. Add juice and zest of lemon, the cinnamon and cloves, heat gently.
4. Stir in the cornflour, egg yolks and butter. Cook over a low heat to thicken, do not boil.
5. Line the flan case with the pastry and bake blind in a preheated oven 200C/400F/Gas 6 for 10-15 minutes. Leave to cool.
6. Place the apple mixture into the flan case, reduce the heat to 180C/350F/Gas 4 and bake for 20 minutes until set. Remove from the oven.
7. Whisk egg whites with 180g/6oz sugar until stiff. Mix the remaining sugar with the ground walnuts.
8. Add the remaining sugar and walnuts to the meringue and mix for 10 seconds. Stop.
9. Pile the meringue on top of the flan and bake in the oven for 10-15 minutes until golden. Cool and serve.