Process sugar, almonds, flour, and butter together then add the egg.
Wrap the pastry in clingfilm and chill well.
Roll out to fit a buttered 23cm loose-bottom flan tin.
Prick the base and chill for at least 3 hours or overnight.
Sprinkle semolina over the pastry and scatter 750g of blackberries on top.
Spoon warmed dulce de leche over the berries.
Mix flour, oatmeal, sugar, and rub in butter to create crumble topping.
Sprinkle crumble over berries and press down lightly.
Bake at 200°C for 15 minutes then reduce to 180°C for 25 minutes.
Poach remaining blackberries in Drambuie and sugar for 3 to 5 minutes.
Serve warm tart with poached berries and thick cream.