Preheat the oven to 190C/375F/Gas 5. Grease and flour a 23cm/9in loose-bottomed tart tin.
Roll out the pastry onto a lightly floured work surface to form a circle a few inches larger than the tart tin. Line the tart tin with the pastry, gently pressing into the edges. Trim the excess pastry from the edge of the tart tin.
Carefully spread the raspberry jam evenly over the pastry base. Lightly crush 3-4 of the raspberries in a small bowl and scatter the crushed berries on top of the jam.
In a large mixing bowl, cream together the butter and sugar until pale and fluffy.
Gradually add the eggs, one at a time, beating each well to incorporate. Stir in equal amounts of the ground almonds after you add each egg, stirring well until combined. Continue until all the eggs and all the ground almonds are used up, then stir in the almond essence.
Pour the filling mixture into the pastry case and, using a palette knife, gently spread it evenly over the raspberry layer.
Bake the tart on the middle shelf of the oven for 35-40 minutes, or until the surface is golden-brown.
Dust with icing sugar and serve with the remaining raspberries and a dollop of clotted cream.