In a large bowl, whisk together flour, sugar, baking powder, baking soda, and salt. In a medium bowl, whisk together eggs, milk, sour cream, melted butter, and vanilla; add to flour mixture. Fold in 1 c. blueberries.
Heat a griddle over medium-high heat. Pour 1/4 c. batter on to heated griddle; flip after 1 minute, or when bubbles begin to pop. Continue to cook for another minute, or until golden brown.
Prepare syrup by bringing butter, sugar, buttermilk, and Karo syrup to a boil in a large pot. Remove from the heat and stir.
Add baking soda and vanilla. The mixture will fizz to twice the size. Stir occasionally and serve warm over prepared pancakes.