Rub flour and butter together with fingertips until crumb like texture forms. Add a pinch of salt and enough cold water to bring mixture to a smooth dough.
Wrap in cling film and leave in fridge for at least 30 minutes.
When ready, roll out pastry on a floured surface and use to line a greased 20-23cm/8-9" round tin.
For the filling, place butter and sugar into a bowl and blend into a creamy paste.
Add the ground almonds, eggs and almond essence and whisk until smooth and creamy.
Spread the raspberry jam onto pastry base, then pour in the filling.
Place in a preheated oven at 200°C/400°F/Gas 6 for 25-30 minutes until lightly golden brown on top. Sprinkle flaked almonds on top 5 minutes before the end of baking time to lightly toast.
Leave to rest and cool slightly for 20 minutes. Serve with a dollop of cream, custard or crème fraîche.
