Puree the blackberries with a jug or stick blender and rub through a sieve to extract as much of the juice as possible. Place the sieve directly over a medium heavy based saucepan to minimise washing up.
Add the condensed milk and warm it up on a low heat, stirring all the while.
Add the rose syrup.
Increase the heat a little and add the milk powder. Whisk until any lumps that have formed, disappear.
Add the desiccated coconut and continue to stir.
Cook for about an hour, stirring every few minutes until the mixture looks fairly dry and as though it might be thick enough to set.
Spoon into a 2 lb loaf tin lined with baking paper and smooth down with the back of a spoon.
Leave for at least a couple of hours to set.
If you opt for the chocolate drizzle, melt the chocolate in a bowl suspended over hot, but not boiling, water.
Turn the barfi out onto a board.
Drizzle the chocolate over the barfi with a teaspoon.
Cut into 32 squares.
Please note: calories and other nutritional information are per serving. They're approximate and will depend on exact ingredients used.