Preheat the oven to 140°C/fan 120°C/gas mark 1. Line a large baking sheet with baking paper.
In a large clean bowl, whisk the liquid from the chickpeas with the cream of tartar with an electric hand whisk until it forms stiff peaks. This will take longer than whisking egg whites. Once stiff, gradually add the caster sugar, a spoonful at a time, and continue to whisk for 10-15 minutes until glossy and firm.
Spoon 6 blobs of mix on to the baking paper and bake in the oven for 1 hour. Turn the oven off, leave it ajar and leave the meringues to cool in the oven.
Spoon the firm coconut milk out of the tin into a bowl, leaving the liquid behind. Add the icing sugar and vanilla extract, and whisk until soft peaks form. Top the cooled meringue with the coconut cream, blackberries and chopped chocolate.