Preheat oven to 350 degrees.
Lightly coat muffin tin with cooking spray or oil.
Mash or puree bananas in large bowl, then add yogurt, syrup and extract.
Add flour, baking soda and salt.
In separate bowl, lightly coat blackberries in flour and shake off excess.
Gently fold berries into banana and flour mixture.
Scoop batter into muffin tin.
Sprinkle tops of muffins with light coating of raw sugar crystals, if desired.
Bake for 20 minutes until muffin tops are golden brown.
Cool on rack for 5 minutes.