Blackberries are a true autumn treat and they're especially tasty when you've spent the afternoon picking them yourself. You probably had your hands and sleeves shredded by the brambles, but now you can look forward to a truly tasty pudding!
That said, I often find blackberries a little too sweet for my liking, so when I make blackberry crumble I either add a couple of chopped sour apples to the berries or I sharpen the fruit with the juice of half a lemon. If you have a sweet tooth or you've picked your blackberries when they were just ripe and still retain some acidity, then you need not bother.
As all crumbles, blackberry crumble is very good-natured, looking after itself in the oven while you soak in the bath trying to scrub the purple stains from your face and fingers.
It's rarely possible to gauge exactly how many berries you've picked, but fortunately exact measurements are moot when making crumble. You want about a pound (500g) of fruit, but a bit this way or that matters very little.
Wash the berries well but carefully so you don't squash them too much, and pick them over. Pinch off all stems, even the recalcitrant ones, then pile all the fruit into a baking dish.
If your blackberries are very tart, sprinkle with 1-2 tablespoons of sugar. If they're too sweet add a peeled chopped Bramleys apple, or the juice of half a lemon.
In a separate bowl rub together 2 parts white flour with 1 part butter and 1 part sugar until the mixture resembles fine crumbs. A food processor or mixer makes short work of this.
The actual quantities for your crumble topping depend on the size of your baking dish. Mine takes 200g flour / 100g butter / 100g sugar and 500g of fruit. To make the topping crunchier, replace 50g of the flour with 50g ground almonds or 50g fine semolina.
Spread the crumble mix over the blackberries and bake in a medium
oven (180°C or so) for about 30 mins. The crumble is ready when the
topping is golden and crunchy and the juices from the fruit have started
to bubble through the crust.
Blackberry crumble is excellent with hot, thick custard or even vanilla ice cream, if your teeth can take it.
There's a bit of an argument here amongst crumble aficionadoes. Some like a really deep layer of fruit with just a bit of topping, others prefer the crunchy pastry, speckled with caramelised fruit juice. Personally, I use a medium-sized ceramic baking dish for my rhubarb crumble. I place the fruit tightly but almost in a single layer and cover it with a thick layer of crumble topping.