Roll the dough out into a long rectangular shape with the shorter sides about half the length of the longer sides. Have the shorter length towards you. Most methods for making buns usually state that you should roll the long side; however, this time, I wanted super thick buns and did it this way for that reason.
Spread the blackberry mixture all over the dough, leaving approximately a 1cm edge all the way round.
Very carefully, roll up from the edge facing you, as tight as you can, until you have a fat roll. Place the seam facing down.
Slice into 6 or 8 buns (depending on how large you want them).
Grease a fairly small skillet or baking dish.
Place the buns very close to each other. There should be space for all of them to fit in but it will be a squeeze. This forces the bread to rise up rather than spread out, resulting in higher buns.
Overnight buns: cover the buns with clingfilm, and place in the fridge. In the morning, pre-heat the oven to 200°C (400℃) and allow the buns to come up to room temperature (I usually sit the dish on top of my oven as it's heating up).
If baking immediately: pre-heat the oven to 200°C (400℃). Cover the buns with a tea-towel, and leave them to rest for around 30 minutes.
Bake for around 20 minutes. Don't be alarmed if some of them really pop up and the blackberries ooze out - it's all part of the charm. The buns are ready when they are a nice golden brown colour on top.
Remove from the oven and allow to cool for a while.