Cream together the butter and sugar. Add the beaten egg and 2 tablespoons of the flour and mix thoroughly. Add the remaining flour and cinnamon and combine to form a homogeneous mixture. If using a food processor, you should process it to the 'crumb' stage, then bring it together by hand. Wrap the pastry in clingfilm and leave in the fridge for 30 minutes. Roll the pastry out between two sheets of floured greaseproof paper and line a 30cm-square baking tray. Chill.
Peel, core and dice the apples into 1cm cubes, place them in a saucepan with the sugar and 2 tablespoons of water, then cover with a lid. Bring to the boil and cook with the lid on for 8 minutes. Remove the lid and cook for a further 10 minutes over a low heat to evaporate a little of the liquid. Mix in the blackberries and leave to cool.
To make the topping, combine all the dry ingredients. Melt the butter with the honey, add to the dry ingredients and mix well.
Spread the cooled blackberry and apple onto the pastry base. Sprinkle the topping over the fruit. Bake at 200°C/gas mark 6 for 15 minutes, reduce the heat to 180°C/gas mark 4 and bake for a further 20-25 minutes. The topping should be golden-brown and crunchy. Serve warm or cold, dusted with icing sugar, and cut into squares. Delicious served with roasted apple ice cream, clotted cream or crème fraîche.