Heat jam until liquid, then stir in remaining ingredients, until berries are coated evenly with sauce.
Put first three ingredients into food processor. Using pulse button, cut butter in coarsely, then add mixed milk and vinegar slowly unitl mixture will form a dough. Do not overmix. Cut ball of dough in two. Roll each half thinly, to form a 25cm circle. Cut one circle into 10 strips.
Line a 20cm sponge sandwich tin with the whole circle of pastry, allowing pastry to overlap dish by about 2cm. Pile filling into uncooked crust. Dampen pastry edges with water. Arrange pastry strips in a lattice pattern over the filling, then turn in the overlapping edges of the pastry circle to enclose the ends of the strips. Bake at 210 degrees Celcius until pastry is golden brown; 25-40 minutes. Serve warm.