Preheat the oven to 180'C. Sift the flour into a bowl and then grate in the butter. Work together with your fingertips until the mixture resembles breadcrumbs. Make a well in the centre and add the water. Bring the dough together but take care not to overwork it. Once the dough forms a ball, flatten slightly, wrap in cling film and chill in the fridge for at least half an hour.
Butter and line an 8 inch cake or tart tin.
Roll the pastry out and use to line the tin. Prick the pastry with a fork and then line with baking parchment. Add baking beans and bake blind for 20-25 minutes. Remove the baking beans, brush the pastry with egg wash and return to the oven for a 10 minutes or until the pastry is just cooked all over.
Once the pastry case is cooked, lower the oven temperature to 160'C.
Beat the butter and caster sugar together until pale and fluffy. Beat in the egg and then add the ground almonds and the almond extract. Fold in the flour, lemon juice and milk. Whisk the egg white until fluffy and gently fold into the mixture.
Spread the plum jam over the pastry base and spoon the almond mixture on top. Smooth the mixture to a level and then sprinkle the flaked almonds on top. Transfer to the oven and bake until golden brown and firm on top - about 30 minutes. Leave to cool in the tin for 10 minutes before removing and leaving on a wire rack to cool.
Cut into slices and serve with cream.
«This tart can very easily be prepared in stages in advance - make the pastry a day in advance and chill overnight and then make the filling with it is blind baking. Try adding some chopped prunes to add even more flavour to this tart.»