Sift the flour and cinnamon into a bowl and make a well in the centre. Add the egg and milk, working them into the flour to form a smooth batter. Stir in the apple.
Heat the blackberries with 2 tablespoons of water in a small saucepan. Bring to a simmer, then sprinkle the caster sugar into the pan and stir until dissolved. Cook for 2–3 minutes until the juices become syrupy and the blackberries have softened, but still hold their shape. Remove from the heat.
Melt the butter in an 18cm non-stick frying pan, swirling it around to coat the base and side. Pour off the excess and reserve. Drop 1 1/2 tablespoons of batter into the pan, and shake the pan to ease the mixture over the base. Cook until crisp and nutty brown at the edges, then flip over with a spatula and cook the other side until browned. Keep warm.
Repeat to make six pancakes in total, greasing the pan with the reserved butter. Serve warm, sprinkled with a little caster sugar and topped with a spoonful of the blackberries and syrupy juices, with your choice of accompaniment.
• Both the pancakes and the blackberry compote can be frozen in separate airtight containers. Before freezing, interleave the pancakes with pieces of baking paper. • You can use 2 tablespoons of apple juice to cook the blackberries instead of water.