Mix the blackberries, blueberries, vanilla, sugar and water in a medium pan, over medium heat. Cover the pan with a lid and let it boil gently for a few minutes until the fruits are soft.
Cut 4 nice thick slices of bread and toast your bread light brown in the oven or toaster.
When the fruits in the pan are soft you can mash them with a fork. Make a porridge of 2 tablespoonscornstarch and some water. Pour this into the fruit while stirring and let it soak up completely in theliquid, so that your sauce becomes a little firmer.
Spread a thick layer of Bettine goat cheese spread over the toasted bread and spoon the warm mixture from the pan over your bread. Finish with a mint leaf and serve immediately.