- Put all the pastry ingredients in a food processor and blitz until they just start to come together. Turn the pastry out on to a cool work surface, pat into a ball, wrap in greaseproof paper and refrigerate for 45 minutes to an hour. 
- Meanwhile, in a stand mixer cream the butter and sugars for three or four minutes, until light and fluffy. Beat in the eggs one at a time, mixing each one in well before adding the next, then fold in the vanilla, salt and ground almonds. 
- Heat the oven to 200C (180C fan)/390F/gas 6. Roll out the chilled pastry on a lightly floured surface into a 26cm square. Butter a 26cm x 26cm square baking tin and lay the pastry on top, gently pushing it into the corners and edges. 
- Spread the jam evenly over the pastry, followed by the almond mix, smoothing it out with a palette knife. Dot the blackberries over the top, pushing them gently into the batter, then scatter over the flaked almonds. Bake for 35-40 minutes, until golden and set, then remove and leave to cool in the tin.