Preheat oven to 400°. Place first 4 ingredients in a blender; process just until smooth., Pour melted butter into a 13x9-in. baking dish; tilt dish to coat. Add batter; bake, uncovered, until puffed and golden brown, about 20 minutes., Meanwhile, place butter, sugar, buttermilk, corn syrup and baking soda in a small saucepan; bring to a boil. Cook, uncovered, 7 minutes. Remove from heat; stir in vanilla., Remove pancake from oven. Dust with confectioners' sugar; serve immediately with syrup and, if desired, fresh blueberries.