Add the flour, butter and sugar to a bowl and rub together with your fingertips until it looks like fine breadcrumbs
Add the egg and almond essence and bring together into a dough
Roll out on a lightly floured surface to about 3–4mm thick and use to line the base of your tin
Chill in the fridge for 20 minutes
Preheat your oven to 180°C (160°C fan)
Spread the raspberry jam evenly over the chilled base
Beat the butter and sugar together until pale and fluffy
Add the eggs one at a time, beating well after each
Mix in the almond essence
Fold in the ground almonds and self-raising flour
Pour in the milk and mix until smooth and creamy
Spoon or pipe the frangipane over the jam layer and gently spread evenly
Sprinkle generously with flaked almonds
Bake for 20–25 minutes until golden and set in the centre
Leave to cool completely in the tin
Chill in the fridge for 30 minutes before slicing into squares
