Serves: About 8 waffles
For the berry syrup: Combine 1/2 cup blackberries, 1/2 cup blueberries and the syrup in a small saucepan. Bring to a simmer over medium heat and cook, stirring occasionally, until the berries begin to pop and the syrup reduces slightly, about 8 minutes. Remove from the heat and stir in the remaining berries. Cover and keep warm.
For the waffle batter: Preheat a waffle iron to medium-high if there are settings (but it's ok if there aren't any). Preheat the oven to 95°C (to keep cooked waffles warm). Whisk together the flour, cornmeal, sugar, baking powder, baking soda, cinnamon, salt and corn kernels in a large bowl. Whisk together the buttermilk, vanilla, eggs and butter in another bowl. Fold the buttermilk mixture into the flour mixture until just combined (it's ok if there are lumps).
Lightly brush the top and bottom of the waffle iron with butter, then fill each section about three-quarters of the way full (there should still be some waffle iron showing). Close and cook until the waffles are golden brown and slightly crisp, 6 to 10 minutes. Keep waffles warm in the oven or covered with foil on a plate while you repeat with the remaining batter.
Drizzle each waffle with berry syrup.