You will need
for base and topping:14oz/390g plain flour
7oz/200g caster sugar
12oz/340g butter, chilled and cut into small cubes
for the filling4 large eggs
9oz/260g caster sugar
300ml (one large pot) sour cream
3.5oz/100g plain flour
1tsp Vanilla extract
zest of half a lemon
1 1/2lb/700g fresh blackberries
Preheat oven to 350F/180C/GAS4
Start with the base - sift the flour, sugar and salt into a large bowl then rub in the butter until the mixture resembles rough breadcrumbs. Reserve approx 200g of this mixture for the topping and press the remaining mixture into the base of a large tray bake tin (I used a large roasting tray measuring approx 43cm x 32cm). Pop this in the oven for 12-15mins to set the base. Remove from the oven and allow to cool whilst preparing the filling.
Whisk the eggs in a large bowl then add all the other ingredients except the blackberries, mixing thoroughly. Finally fold in the blackberries gently.
Pour the mix over the base then top with the remaining crumble mix.
Bake in the oven for approx 50mins.
Blackberry Crumble Pie tastes just wonderful warm from the oven served with cream, custard or ice cream but works even better if you leave it cool completely, cut it into squares and refrigerate. The centre firms up nicely and contrasts beautifully with the buttery crumble top and bottom. It will keep in the fridge for up to a week in a covered container.
Best of all this tray bake freezes well too which is just as well as this recipe makes a lot of pie! Cut into slices/squares when cold and freeze in suitable containers. Defrost for about 4 hours before serving.